Laser questions

Which type of emission, spontaneous or stimulated, is dominant in the light source shown in the figure?

1. A Spontaneous emission
2. B Stimulated emission
3. C Both occur equally
4. D The information is not enough to decide

The ratio between the lifetime of an atom in an unstable excited level and its lifetime in a metastable level is ..........

1. A greater than one
2. B equal to one
3. C less than one
4. D the information is not enough to decide

In a neon lamp ..........

1. A the dominant emission is photoelectric emission
2. B the dominant emission is spontaneous emission
3. C the dominant emission is stimulated emission
4. D spontaneous and stimulated emission occur equally

The opposite figure shows two atoms X and Y of an active medium. If a photon of energy $(E_2 - E_1)$ passes by each of them, the process that takes place in each is ..........

1. A X: spontaneous emission, Y: stimulated emission
2. B X: absorption, Y: stimulated emission
3. C X: stimulated emission, Y: spontaneous emission
4. D X: spontaneous emission, Y: absorption

The opposite diagram shows an excited atom whose lifetime has not ended yet. What is the energy of the photon that causes stimulated emission from it?

1. A 3.4 eV
2. B 10.2 eV
3. C 13.6 eV
4. D 17 eV

The following figures show the waves accompanying the motion of photons. Which pair of these waves belongs to two coherent photons?

1. A A
2. B B
3. C C
4. D D

The opposite figure represents the process of ..........

1. A spontaneous emission
2. B spontaneous absorption
3. C stimulated emission
4. D stimulated absorption

The opposite figure represents a case of ..........

1. A spontaneous emission
2. B stimulated emission
3. C absorption
4. D population inversion

The opposite figure shows an atom excited to the energy level $E_1$. Which of the following statements gives the condition needed for stimulated emission from this atom?

1. A Its lifetime in level $E_1$ ends
2. B A free electron of energy $(E_1 - E_0)$ collides with it
3. C A photon of energy $(E_1 - E_0)$ falls on it
4. D Another atom excited to level $E_1$ collides with it

Which of the following cases can represent an atom in which stimulated emission takes place by a photon of energy E?

1. A A
2. B B
3. C C
4. D D

Spontaneous emission of a photon from an excited atom takes place ..........

1. A when a photon falls on an excited atom
2. B by the effect of a low-frequency photon
3. C without any external effect
4. D by the effect of a high-frequency photon

In the opposite figure, two atoms (x) and (y) of the same element were excited together at the same instant to level $(E_1)$. When they return to their ground level $(E_0)$, atom (x) returns and emits a photon by spontaneous emission, and atom (y) returns by the effect of an external photon and emits a photon by stimulated emission. Which of the following is different for the two atoms (x) and (y)?

1. A The energy of the photon emitted from the atom
2. B The time the atom spends in level $(E_1)$
3. C The speed of the photon emitted from the atom
4. D All of the above are the same for both atoms

Two atoms (1) and (2) of the same element were each excited to an energy level whose lifetime is $10^{-3}$ s. If they returned to the ground level after spending $10^{-5}$ s and $10^{-3}$ s respectively in the excited level, this happened ..........

1. A atom (1): by an external photon, atom (2): by an external photon
2. B atom (1): by an external photon, atom (2): without any external effect
3. C atom (1): without any external effect, atom (2): by an external photon
4. D atom (1): without any external effect, atom (2): without any external effect

The graph that represents the relation between the radiation intensity of an electric lamp and the square of the distance $(d^2)$ the radiation travels away from the lamp is ..........

1. A A
2. B B
3. C C
4. D D

The graph that represents the relation between the radiation intensity of a laser source and the distance (d) the radiation travels away from the source is ..........

1. A A
2. B B
3. C C
4. D D

The ratio between the speed of a laser beam in vacuum and the speed of light from ordinary sources in vacuum is ..........

1. A greater than one
2. B less than one
3. C equal to one
4. D cannot be determined

The property common to laser photons and X-ray photons is that they ..........

1. A are coherent
2. B are monochromatic
3. C have the same speed in vacuum
4. D have the same energy

A surface is illuminated by different light sources of the same light power from the same distance. The illumination intensity on the surface is greatest when using ..........

1. A light from a tungsten lamp
2. B light from a fluorescent lamp
3. C light from a neon lamp
4. D laser light

Laser rays do not obey the inverse square law of light because their photons ..........

1. A are coherent
2. B scatter on air particles
3. C have a single wavelength
4. D have a large divergence angle

A laser light beam is parallel, which means that its photons have the same ..........

1. A direction
2. B frequency
3. C intensity
4. D wavelength

Which of the following figures represents a (helium-neon) laser beam passing through an equilateral triangular prism in the position of minimum deviation?

1. A A
2. B B
3. C C
4. D D

If the intensity of a laser beam 10 cm from its source is I, its intensity 20 cm from the source is ..........

1. A 2 I
2. B I
3. C $\dfrac{I}{2}$
4. D $\dfrac{I}{4}$

In the figure shown, if the laser source is switched on, the ratio between the intensity of the laser beam at points x and y $\left(\frac{I_x}{I_y}\right)$ is ..........

1. A $\dfrac{1}{1}$
2. B $\dfrac{4}{1}$
3. C $\dfrac{1}{4}$
4. D $\dfrac{2}{1}$

The opposite figure shows the path of ordinary light rays. The ratio between the amplitude of the light wave at point y and its amplitude at point x $\left(\frac{A_y}{A_x}\right)$ equals ..........

1. A $\dfrac{1}{2}$
2. B $\dfrac{1}{4}$
3. C $\dfrac{1}{8}$
4. D $\dfrac{1}{16}$

The opposite figure shows two identical flat surfaces (x, y) placed at different distances ($d_1$, $d_2$) on both sides of a light source. If the illumination intensity on surface (x) is 2.25 times that on surface (y), the ratio $\left(\frac{d_1}{d_2}\right)$ equals ..........

1. A $\dfrac{1}{2}$
2. B $\dfrac{4}{9}$
3. C $\dfrac{2}{3}$
4. D $\dfrac{3}{4}$

Laser rays are monochromatic because ..........

1. A all atoms of the active medium are excited to a single unstable energy level
2. B all atoms of the active medium are in the ground energy level
3. C all photons emitted by stimulated emission have the same energy
4. D all photons emitted by stimulated emission are amplified as they pass between the two reflecting mirrors

Two spectra (x) and (y): spectrum (x) is of a laser and spectrum (y) is of ordinary light. Each was analysed separately by a spectrometer. Which of the following graphs can express the relation between intensity (I) and wavelength (λ) for the two spectra?

1. A A
2. B B
3. C C
4. D D

All of the following are true about producing a laser except that ..........

1. A spontaneous emission takes place in some atoms during production
2. B the intensity of the laser beam changes with the reflection coefficient of the partially transparent mirror
3. C producing a laser does not need an external energy source
4. D the atoms of the laser's active medium have a metastable energy level

Optical pumping in a laser aims to achieve ..........

1. A a stable state
2. B population inversion
3. C a state of equilibrium
4. D amplification of the laser beam

In the laser action, the step that follows pumping is ..........

1. A a stable state of the atoms
2. B population inversion
3. C equilibrium between the atoms
4. D amplification of the laser beam

The following figures show how the atoms of an active medium are distributed among their energy levels. Which of them can represent the atoms reaching population inversion? (Note: level $E_1$ is the ground level.)

1. A A
2. B B
3. C C
4. D D

Optical pumping is used in the .......... laser.

1. A carbon dioxide
2. B helium-neon
3. C fluorine-hydrogen
4. D ruby

Optical pumping by a laser beam is used to produce a laser whose active medium is ..........

1. A gas molecules
2. B a solid crystal
3. C a semiconductor
4. D a liquid dye

The (helium-neon) laser lies in the region of ..........

1. A infrared rays
2. B ultraviolet rays
3. C visible light
4. D X-rays

A spectrometer was used to analyse the light emitted from several light sources. Which of the following pictures represents the image formed in the spectrometer for (helium-neon) laser light?

1. A A
2. B B
3. C C
4. D D

In the (helium-neon) laser, the laser photons are emitted from the atoms of ..........

1. A helium
2. B neon
3. C both helium and neon
4. D quartz

To produce a laser in the (helium-neon) laser, it is necessary to ..........

1. A raise the pressure inside the tube above atmospheric pressure
2. B decrease the potential difference of the source
3. C make the proportion of helium atoms greater than that of neon atoms
4. D illuminate the tube with neon light

In the (helium-neon) laser, the element whose atoms reach population inversion as one of the steps of producing laser photons is ..........

1. A helium only
2. B neon only
3. C both helium and neon
4. D sometimes helium and sometimes neon

In the (helium-neon) laser, one of the steps of producing the laser is that an excited helium atom loses its excitation energy by colliding with ..........

1. A another stable helium atom
2. B the walls of the electric discharge tube
3. C an unexcited neon atom
4. D an excited helium atom

Which of the following figures correctly shows the external resonant cavity in a (helium-neon) laser?

1. A A
2. B B
3. C C
4. D D

Which of the following correctly represents the properties of the components of a (helium-neon) laser?

1. A A
2. B B
3. C C
4. D D

The opposite figure represents a (helium-neon) laser. Which of the components shown is the main cause of amplification?

1. A Component (1)
2. B Component (2)
3. C Component (3)
4. D Components (1) and (2)

The opposite figure shows the structure of a (helium-neon) laser. If the laser beam comes out of mirror (1), then the reflection coefficient of mirror (1) compared to that of mirror (2) is ..........

1. A greater
2. B smaller
3. C equal
4. D cannot be determined

The opposite diagram shows a (helium-neon) laser and four photons (A, B, C, D) emitted in different directions inside the tube. Which of these photons can stay moving inside the tube for the longest time before it comes out?

1. A Photon A
2. B Photon B
3. C Photon C
4. D Photon D

The opposite figure represents a (helium-neon) laser. If component (x) stops working ..........

1. A the radiation intensity decreases
2. B the radiation frequency decreases
3. C the speed of the beam decreases
4. D no laser beam is produced

The opposite figure shows the energy levels of the atoms of the active medium in a (helium-neon) laser. When helium atoms in energy level $E_3$ (a metastable level) collide with unexcited neon atoms, the neon atoms are excited to level .......... so that population inversion is reached.

1. A $E_0$ only
2. B $E_1$ only
3. C $E_2$ only
4. D $E_1$ and $E_2$ together

The opposite figure represents the energy levels of a neon atom. When the atom gained energy $(E_x)$ it was excited to a certain level, and before its lifetime in this level ended another photon of energy $(E_y)$ passed by it, so the atom emitted a photon by stimulated emission whose energy equals that of a (helium-neon) laser photon. The energies of the two photons $E_x$ and $E_y$ are ..........

1. A $E_x$: $E_1 - E_0$, $E_y$: $E_1 - E_0$
2. B $E_x$: $E_1 - E_0$, $E_y$: $E_2 - E_1$
3. C $E_x$: $E_2 - E_0$, $E_y$: $E_2 - E_0$
4. D $E_x$: $E_2 - E_0$, $E_y$: $E_2 - E_1$

The opposite diagram represents the energy levels of helium and neon atoms. The largest energy difference between these levels is for a transition between the two levels ..........

1. A $E_3$, $E_1$
2. B $E_2$, $E_1$
3. C $E_1$, $E_0$
4. D $E_0$, $E_2$

The opposite figure shows some transitions x, y, z, k in a (helium-neon) laser. The correct time order in which these transitions happen is ..........

1. A k then y then z then x
2. B x then y then z then k
3. C x then k then z then y
4. D z then y then x then k

The opposite figure represents the energy level diagram of a (helium-neon) laser:
(1) The energy needed to excite helium atoms equals ..........

1. A 18.7 eV
2. B 20.61 eV
3. C 20.66 eV
4. D 21 eV

The opposite figure represents the energy level diagram of a (helium-neon) laser:
(2) The energy of the emitted laser photons equals ..........

1. A 0.68 eV
2. B 1.96 eV
3. C 3.12 eV
4. D 4.05 eV

The opposite diagram represents a (helium-neon) laser. Which of the parts shown is the component in which population inversion takes place?

1. A (1)
2. B (2)
3. C (3)
4. D (1), (2)

The property that allows laser rays to be used in holography is that ..........

1. A its photons are coherent
2. B its rays are parallel
3. C it keeps a constant intensity
4. D it has a high intensity

A laser beam of wavelength λ was used in holography, and the phase difference between two of the rays reflected from the object was $\frac{\pi}{2}$. The path difference between them is ..........

1. A $\dfrac{\lambda}{4}$
2. B $\dfrac{\lambda}{2}$
3. C 2 λ
4. D 4 λ

The opposite figure represents two laser waves reflected from two points A and B on an object in holography. If the path difference between them is 3164 Å, the wavelength of the laser equals ..........

1. A 1582 Å
2. B 3164 Å
3. C 4746 Å
4. D 6328 Å

The opposite figure shows how an image of an object is formed on a photographic plate:
(1) The group of rays that differ from each other in intensity is group ..........

1. A (1)
2. B (2)
3. C (3)
4. D (4)

The opposite figure shows how an image of an object is formed on a photographic plate:
(2) The group of rays that differ from each other in phase is group ..........

1. A (1)
2. B (2)
3. C (3)
4. D (4)

The opposite figure shows how an image of an object is formed on a photographic plate:
(3) The image formed on the photographic plate is ..........

1. A similar to the object and two-dimensional
2. B similar to the object and three-dimensional
3. C coded as interference fringes
4. D similar to the object and magnified

Measuring long distances using laser rays depends on the property of ..........

1. A the spectral purity of the laser
2. B the parallelism of laser rays
3. C the heating effect of laser rays
4. D the high speed of the laser

The laser is used to reattach a detached retina depending on ..........

1. A the coherence of its photons
2. B its heating effect
3. C its spectral purity
4. D its high speed

The following diagrams show an atom moving between two of its energy levels. Show, with explanation, which of these diagrams represents:
(1) absorption.
(2) stimulated emission.
(3) spontaneous emission.

Stimulated emission involves producing another photon identical to the incident photon. Show whether getting these two photons breaks the law of conservation of energy.

Explain: laser rays do not obey the inverse square law.

In the opposite figure, a laser source and an electric lamp of the same light power are placed at the same large distance from a screen. Compare the intensity of the laser light and the intensity of the lamp light on the screen, and explain your answer.

If the intensity of light from a tungsten lamp 1 m from the source is $16\ mW/m^2$, what is the intensity of this light 2 m from the source?

In the (helium-neon) laser, what is the function of each of:
(1) the neon atoms?
(2) the electric voltage source?

While researching laser production, scientists found that the efficiency of producing a laser is very high when helium atoms are added to neon atoms in a certain ratio, instead of using neon atoms alone in the tube. Explain the role of the helium atoms.

In the opposite figure, describe, with explanation, the spectrum formed on the screen if the light source is:
(1) a (helium-neon) laser.
(2) a tungsten lamp.

How does amplification take place in a (helium-neon) laser?

Give a reason: an X-ray photon has more energy than a (helium-neon) laser photon, yet (helium-neon) laser rays can reach farther distances than X-rays.

State one similarity and one difference between: (helium-neon) laser photons and X-ray photons.

Explain why, when a (helium-neon) laser beam falls on a metal surface, no photoelectrons are emitted despite the high concentration of the beam, while when white light falls on the same surface, photoelectrons are emitted.

What happens when a hologram is illuminated by a laser beam of the same wavelength as the reference rays, and you look through it with the naked eye?

In the opposite figure, how do the properties of the beam reflected from the object differ from those of the beam falling on it?

What is the condition for recording the surface shape of an object on a photographic plate?

Why are laser rays used in each of:
(1) guiding missiles in military applications?
(2) holography?
(3) treating a detached retina?

The diagram shows a (helium-neon) laser device. (Trial exam / June 2021)
What is the role of the components shown in the figure?

1. A 1- producing photons 2- making a high potential difference 3- reflecting photons
2. B 1- reflecting photons 2- containing the active medium 3- making a high potential difference
3. C 1- pumping excitation energy to the atoms 2- exciting neon atoms 3- amplifying photons
4. D 1- producing laser photons 2- the energy source used 3- exciting neon atoms

In the chromium-doped ruby laser, powerful xenon lamps are used to excite the atoms of the active medium. (Trial exam / June 2021)
So $\frac{\text{speed of the laser beam}}{\text{speed of xenon lamp light in air}}$ ...

1. A is greater than one
2. B equals zero
3. C is less than one
4. D equals one

The figure shows a diagram of a helium-neon laser device. (1st session 2021)
Which choice correctly gives the parts with an important role in amplifying the laser photons?

1. A (1) , (2)
2. B (1) , (4)
3. C (4) , (5)
4. D (3) , (5)

A laser beam has radius (r) and intensity (I) at its source. (1st session 2021)
Its intensity and its diameter 15 m from the source ...

1. A intensity: does not change, diameter: does not change
2. B intensity: increases, diameter: increases
3. C intensity: decreases, diameter: decreases
4. D intensity: decreases, diameter: increases

A photon of frequency ν fell on an excited atom as in the opposite figure. (Trial exam / June 2021)
Which of the following figures shows the properties of stimulated emission?

1. A A
2. B B
3. C C
4. D D

The spectral purity of laser rays means that their photons ... (Sample exam 2025)

1. A have one direction
2. B have almost a single wavelength
3. C do not obey the inverse square law
4. D are in phase

The form of energy used to excite the atoms of the active medium in the liquid dye laser is ... (Sample exam 2025)

1. A light
2. B heat
3. C electric
4. D chemical

Helium and neon are chosen as the active medium for producing the (He-Ne) laser because of ... (Sample exam 2025)

1. A the equal number of energy levels in them
2. B the close values of the energies of their stable excited levels
3. C the close values of the energies of their metastable excited levels
4. D all of the above

In the (helium-neon) laser, when the partially transparent mirror (reflection coefficient 95%) is replaced by another one (reflection coefficient 98%), (Sample exam 2025)
the intensity of the resulting laser beam ... and the energy of a single photon of the resulting laser beam ... respectively

1. A changes , stays constant
2. B changes , changes
3. C stays constant , changes
4. D stays constant , stays constant

In the helium-neon laser, when the partially transparent mirror is replaced by a transparent glass plate, which of the following choices is correct? (2nd session 2024)

1. A The intensity of the resulting laser beam rises to a maximum
2. B Population inversion never takes place
3. C No laser beam is produced at all
4. D Stimulated emission never takes place

The laser is used in holography because laser rays are characterised by ... (2nd session 2024)

1. A their high intensity
2. B their effect on photographic plates
3. C the coherence of their photons
4. D having a single wavelength

If the phase difference between two waves reflected from the object in holography equals $\frac{\pi}{4}$, which of the following choices gives the path difference between them? (1st session 2024)

1. A $\frac{\lambda}{2}$
2. B $\frac{\lambda}{4}$
3. C $\frac{\lambda}{8}$
4. D $\frac{\lambda}{16}$

In three-dimensional imaging using the laser, (1st session 2024)
which of the following rays differ from each other in phase?

1. A The rays falling from the light source on the plane mirror
2. B The rays falling from the light source on the object
3. C The rays reflected from the plane mirror to the photographic plate
4. D The rays reflected from the object to the photographic plate

The laser beam starts to come out of the partially transparent mirror in the helium-neon laser depending on ... (2nd session 2023)

1. A the radiation intensity inside the resonant cavity
2. B the proportion of atoms of the active medium in population inversion
3. C the electric potential difference inside the laser tube
4. D the lifetime of the atoms in the metastable level

Using the laser in the military field to destroy missiles depends on ... (2nd session 2023)

1. A the energy of the laser beam
2. B the spectral purity of the laser beam
3. C the coherence of the laser beam photons
4. D the wave nature of laser light

The number of photons is amplified by stimulated emission in the helium-neon laser as a result of the collision of ... (2nd session 2023)

1. A excited neon atoms in the metastable level with each other
2. B excited helium atoms with excited neon atoms in the metastable level
3. C photons reflected from the resonant cavity mirrors with excited neon atoms in the metastable level
4. D excited helium atoms with unexcited neon atoms

If the phase difference between two laser waves after reflection from an object is $2\pi$, (1st session 2023)
the path difference between them is ...

1. A $\lambda$
2. B $2\lambda$
3. C $\pi$
4. D $2\pi$

Two light sources: one emits ordinary monochromatic (blue) light and the other emits a laser in the red region of the spectrum. (Trial exam 2023)
Which of the following statements is correct?

1. A Laser photons are coherent and have higher energy
2. B Ordinary light photons are coherent and have lower energy
3. C Laser photons are not coherent and have higher energy
4. D Ordinary light photons are not coherent and have higher energy

The intensity of a helium-neon laser beam increases ... (Trial exam 2023)

1. A by decreasing the electric potential difference used
2. B by decreasing the proportion of helium atoms to neon
3. C by increasing the rate of repeated reflections inside the resonant cavity
4. D by increasing the pressure of the gas mixture inside the tube

When one of the two resonant cavity mirrors of a laser device is replaced by a piece of transparent glass and the device is switched on again ... (Trial exam 2023)

1. A the laser beam comes out from the side of the transparent plate
2. B no laser beam comes out of the device
3. C the laser beam comes out from the side with the mirror
4. D the laser beam comes out from both sides

In three-dimensional imaging of an object using the laser, the path difference between two laser waves (2nd session 2021)
reflected from the object was $\frac{2}{3}\lambda$,
so the phase difference between these two waves equals ...

1. A $\frac{3\pi}{4}$
2. B $\frac{4\pi}{3}$
3. C $\pi$
4. D $\frac{3\pi}{2}$

In the following figure, for stimulated emission to take place, the energy of photon (X) must be ... (1st session 2022)

1. A $E + E_0$
2. B $E - E_0$
3. C $2(E - E_0)$
4. D $2(E + E_0)$

Diagrams 1, 2, 3 and 4 show the steps of getting laser photons. (2nd session 2022)
The correct order of the steps of getting the laser beam is ...

1. A 1 → 2 → 4 → 3
2. B 4 → 1 → 2 → 3
3. C 2 → 1 → 4 → 3
4. D 1 → 4 → 2 → 3

The following graphs show the relation between radiation intensity and the distance from the source d. (1st session 2022)
The graph that represents a laser beam is ...

1. A 1
2. B 2
3. C 3
4. D 4

The following graphs show the relation between radiation intensity and wavelength $(\lambda)$ for several light sources, drawn to the same scale. (2nd session 2022)
Which graph represents radiation that can be used in holography?

1. A 1
2. B 2
3. C 3
4. D 4

The figure shows population inversion in neon gas and the time each of the five atoms excited to the metastable level $E_2$ has spent there until a certain moment. Assuming that $5 \times 10^{-4}$ s after that moment, photons each of energy $E_2 - E_1$ reach the five atoms shown in level $E_2$, which of the five atoms will be stimulated before their lifetime ends? (2nd session 2022)
(Assume that the lifetime of the metastable level $E_2 = 10^{-3}\text{s}$)

1. A $e_1, e_3$
2. B $e_2, e_4$
3. C $e_2, e_5$
4. D $e_1, e_2, e_5$

The opposite figure shows how a hologram is formed. Which of the following choices represents the reference rays that take part in forming the interference fringes? (1st session 2023)

1. A B , C
2. B A , B
3. C C only
4. D B only

The opposite figure shows the process of producing helium-neon laser photons, given that $E_2$ and $E_3$ are metastable energy levels. (1st session 2023)
Which transition releases a helium-neon laser photon?

1. A 4
2. B 3
3. C 2
4. D 1

The two graphs show the range of two spectra 1 and 2 emitted from two light sources. (1st session 2024)
When the spectrum from each source had travelled a distance d, the intensity of spectrum 2 was 2I and that of spectrum 1 was 2I. If the distance each spectrum travels from the source becomes 2d, the intensities of spectra 1 and 2 respectively are ...

1. A $2I,\frac{I}{4}$
2. B $I,\frac{I}{2}$
3. C $\frac{I}{4},2I$
4. D $I,\frac{I}{4}$

The opposite figure shows an electron in the first level of an atom. (2nd session 2024)
A photon of energy $E=E_4 - E_1$ fell on it, so the electron was excited to a higher level,
and before the lifetime of the electron in that level ended, another photon of energy
$E=E_4-E_3$ fell on the excited electron. Which of the following choices is correct?

1. A The electron returns from N to K and stimulated emission takes place
2. B The electron returns from N to M and spontaneous emission takes place
3. C The electron returns from N to M and stimulated emission takes place
4. D The electron returns from N to K and spontaneous emission takes place

You have four figures showing the stages of producing a laser. Which figure represents population inversion? (1st session 2021)

1. A 1
2. B 2
3. C 3
4. D 4

You have four figures showing the stages of producing a laser. Which figure shows an emission spectrum? (1st session 2021)

1. A 1
2. B 2
3. C 3
4. D 4

You have four figures showing the stages of producing a laser. Which figure shows the idea of atomic spectral purity? (2nd session 2021)

1. A 1
2. B 2
3. C 3
4. D 4

The figure shows the structure of a helium-neon laser. The neon atoms are excited because of ... (2nd session 2021)

1. A their collision with component 2
2. B their collision with excited atoms of component 3
3. C their collision with unexcited atoms of component 3
4. D gaining energy from component 1

The opposite figure shows the structure of a helium-neon device. Which component is responsible for exciting the neon atoms? (1st session 2022)

1. A 1
2. B 2
3. C 3
4. D 4

The energy of a photon of monochromatic green light emitted from an ordinary light source is .......... the energy of a (helium-neon) laser photon. (1st session 2025)

1. A less than
2. B greater than
3. C half
4. D equal to

The diagram shows the transitions of helium and neon atoms between energy levels during laser production. Which two transitions happen when an excited helium atom collides with an unexcited neon atom? (1st session 2025)

1. A transitions 1 , 4
2. B transitions 5 , 3
3. C transitions 3 , 4
4. D transitions 5 , 2

In three-dimensional imaging, a coherent beam of laser rays of wavelength (λ) fell on an object. If the path difference between two laser waves reflected from the object equals (2λ), the phase difference between them equals .......... (1st session 2025)

1. A $3\pi$
2. B $2\pi$
3. C $4\pi$
4. D $6\pi$

A photon of energy $(E_2 - E_1)$ falls on each of the two atoms (X) and (Y) of an active medium as in the opposite figure. What process takes place in each atom? (2nd session 2025)

1. A atom (X): stimulated emission, atom (Y): spontaneous emission
2. B atom (X): spontaneous emission, atom (Y): stimulated emission
3. C atom (X): spontaneous emission, atom (Y): optical pumping
4. D atom (X): optical pumping, atom (Y): stimulated emission

The type of energy used to excite the atoms of the active medium in the ruby laser is .......... (2nd session 2025)

1. A electric energy
2. B light energy
3. C chemical energy
4. D heat energy

A mixture of helium and neon atoms is used to produce a laser of wavelength 632.8 nm. The figure shows a simplified diagram of the energy levels of helium and neon. Between which two energy levels is there an energy difference of $3.141 \times 10^{-19}\ J$? (2nd session 2025)

1. A $(E_4 - E_3)$
2. B $(E_4 - E_0)$
3. C $(E_3 - E_0)$
4. D $(E_2 - E_1)$

The figure shows two images (1) and (2) appearing when laser rays fall on a hologram. Which of the following choices gives the properties of each image? (Sample exam 2026)

1. A image (1): real, image (2): real
2. B image (1): virtual, image (2): real
3. C image (1): real, image (2): virtual
4. D image (1): virtual, image (2): virtual