Photoelectric Effect and Wave Theory of Light

Author:Embibe Experts
12th Haryana Board
IMPORTANT

Important Questions on Photoelectric Effect and Wave Theory of Light

HARD
IMPORTANT

In a Geiger-Marsden experiment, what is the distance of the closest approach to the nucleus of an alpha particle before it comes momentarily to rest and reverse its direction? Given: Kinetic energy of α -particle =7.7meV and Z=79 for gold.

MEDIUM
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At atom of mass M which is in the state of rest emits a photon of wavelength λ. As a result, the atom will deflect with the kinetic energy equal to (h is Planck's constant)

EASY
IMPORTANT

In a photoelectric effect experiment, the slope of the graph between the stopping potential and the incident frequency will be of the order of

EASY
IMPORTANT

For light having frequency more than threshold frequency the number of electrons emitted in photo-electric effect experiment is proportional to

EASY
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Consider a metal exposed to light of wavelength 600 nm. The maximum energy of the electron doubles when light of wavelength 400 nm is used. Find the work function in eV.

EASY
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Consider figure for photoemission.

How would you reconcile with momentum-conservation? Note light (photons) have momentum in a different direction than the emitted electrons.
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EASY
IMPORTANT

In the explanation of photo electric effect, we assume one photon of frequency v collides with an electron and transfers its energy. This leads to the equation for the maximum energy Emax of the emitted electron as

Emax=hv=ϕ0 where ϕ0 is the work function of the metal. If an electron absorbs 2 photons (each of frequency v), what will be the maximum energy for the emitted electron? Why is this fact (two photon absorption) not taken into consideration in our discussion of the stopping potential?

EASY
IMPORTANT

In the explanation of photoelectric effect, we assume one photon of frequency v collides with an electron and transfers its energy. This leads to the equation for the maximum energy Emax of the emitted electron as

Emax=hv=ϕ0 where ϕ0 is the work function of the metal. If an electron absorbs 2 photons (each of frequency v), what will be the maximum energy for the emitted electron?

EASY
IMPORTANT

Monochromatic light of frequency 5.0×1014 Hz is produced by a laser. The power emitted is 3.0×10-3 W. Estimate the number of photons emitted per second on an average by the source. Take h = 6.626×10-34 Js

MEDIUM
IMPORTANT

The wavelength of a spectral line is 4000 Å. Calculate its frequency and energy. Take, c = 3×108 m/sh = 6.6×10-34