Lasers
Physics ⇒ Modern Physics
Lasers starts at 11 and continues till grade 12.
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See sample questions for grade 11
Describe one medical application of lasers.
Describe the function of the partially reflecting mirror in a laser.
Describe the role of mirrors in a laser cavity.
Explain the difference between spontaneous emission and stimulated emission.
Explain why laser beams can travel long distances without spreading much.
A laser emits light at a wavelength of 632.8 nm. Calculate the frequency of the emitted light. (Speed of light c = 3.0 × 108 m/s)
A laser emits light with a photon energy of 2 eV. Calculate the wavelength of the emitted light. (Planck's constant h = 6.63 × 10-34 J·s, c = 3.0 × 108 m/s, 1 eV = 1.6 × 10-19 J)
A certain laser operates with an active medium that has three energy levels: E1, E2, and E3 (E3 > E2 > E1). If the population of E2 is 2.5 × 1018 atoms/m3 and the population of E1 is 1.0 × 1018 atoms/m3, calculate the population inversion (ΔN) between E2 and E1.
Which of the following best describes the coherence of laser light?
(1) Random phase
(2) Constant phase difference
(3) Multiple wavelengths
(4) High divergence
Which of the following is a characteristic of a four-level laser system?
(1) The lower laser level is the ground state
(2) The lower laser level is above the ground state
(3) No population inversion is required
(4) Only two energy levels are involved
Which of the following is a gas laser?
(1) Ruby laser
(2) Helium-Neon laser
(3) Semiconductor laser
(4) Dye laser
Which of the following is a property of laser light that makes it useful in optical fiber communication?
(1) High divergence
(2) Monochromaticity
(3) Low intensity
(4) Incoherence
Fill in the blank: The condition in which the number of atoms in an excited state exceeds those in a lower energy state is called __________.
Fill in the blank: The energy difference between two energy levels in a laser medium determines the __________ of the emitted laser light.
Fill in the blank: The first working laser was demonstrated in the year __________.
Fill in the blank: The He-Ne laser emits light primarily at a wavelength of __________ nm.
True or False: All lasers operate in the visible region of the electromagnetic spectrum.
True or False: In a laser, population inversion is necessary for stimulated emission to dominate over absorption.
True or False: In a laser, the emitted photons are all in phase with each other.
True or False: Semiconductor lasers are commonly used in CD and DVD players.
