Question Library

The energy of light of frequency 2.0 x 10\(^{15}\)Hz is (h = 6.63 x 10\(^{-34}\)Js)

An electron falls from an energy level of -5.44eV to another energy level, E. If the emitted photon is of wavelength 5.68 x 10\(^{-6}\)m, calculate the energy change. [ Plank's constant = 6.63 x 10\(^{-34}\)Js, emitted radiation speed = 3.0 x 10\(^8\)ms\(^{-1}\)]

Infra-red thermometers work by detecting the

Photometer is used to measure

What are cathode rays?

Light of energy 1.12 x 10\(^{-18}\) J is incident on a metal of ejected electrons with maximum energy of 8.0 x 10\(^{-19}\)J. Calculate the threshold frequency of the metal. [h = 6.626 x 10\(^{-34}\)Js]

(a) Mention three facts about photoelectric effect (b) An electric magnetic radiation source of power 6 x 10\(^{-3}\) W emits 1 x 10\(^{16}\) photons per second. The most energetic photo electron ejected from a metal surface is stopped by a potential difference of 2.2V. Calculate the work function of the metal. [ mass of (photon) electrons 9.1 x 10\(^{-31}\) kg, e = 1.6 x 10\(^{-19}\) C] (c) State two factors on which the activity of a radioactive sample depends (d) Cobalt-60 source has an activity of 2.0 x 10\(^6\) Bq and a half-life of 1.8 x 10\(^8\)s. Calculate the number of radioisotope nuclei in the source.

When light of a certain frequency is incident on a metal surface, no photoelectrons are emitted. If the frequency of the light is increased, what happens to the stopping potential?

If the kinetic energy of an electron is 100 eV, what is the wavelength of the de-Broglie wave associated with it? [h = 6.6 x 10\(^{-34}\) J s, e = 1.6 x 10\(^{-19}\)C, m\(_{e}\), = 9.1 x 10\(^{-31}\) kg]

If the frequency of an emitted x-ray is 1.6 x 10\(^{16}\)Hz, the accelerating potential is? [e = 1.6 x 10\(^{-19}\)J, h = 6.63 x 10-\(^{34}\)Js]

Cathode rays are

In photo-emission, the number of photo-electrons ejected per second depends on the?

The ground state energy for the hydrogen atom is 5.44 x 10\(^{-19}\)J. If an electron drops from zero energy to the ground state, calculate the frequency of the emitted radiation. [h = 6.6 x 10\(^{-34}\) Js]

Thermionic emission is the process whereby?

Caesium has a work function of 3 x 10\(^{-19}\)J. The maximum energy of liberated electrons when it is illuminated by light of frequency 6.7 x 10\(^{14}\) HZ is? [h = 6.6 x 10\(^{-34}\)Js]