Physics - Study Mode

[#1051] The energy of a photon varies directly with its
Correct Answer

(B) Frequency

Explanation

Solution: The amount of energy is directly proportional to the photon's electromagnetic frequency and thus, equivalently, is inversely proportional to the wavelength. The higher the photon's frequency, the higher its energy. Equivalently, the longer the photon's wavelength, the lower its energy.

[#1052] A photon of X-ray has energy of 1 keV. A photon of visible radiation has energy of 3 eV. In this context, which one of the following statements is not correct?
Correct Answer

(C) The speeds of both the photons in vacuum are different

Explanation

Solution: The speed of all the electromagnetic radiation are always same and equal to the numerical value 3 x 10 8 m/sec.

[#1053] The threshold frequency is the frequency below which :
Correct Answer

(C) Photo electric emission is not possible

Explanation

Solution: The photoelectric effect is the emission of electrons by substances, especially metals, when light falls on their surfaces. The photoelectric effect will not occur when the frequency of the incident light is less than the threshold frequency as the electrons are unable to gain sufficient energy to overcome the electrostatic barrier of the work function of the metal.

[#1054] Which of the following supports particle nature of photons ?
Correct Answer

(C) Photoelectric effect

Explanation

Solution: Light is made up of photons, so it has some particle properties. In the photoelectric effect, light hits some material which absorbs it, and then ejects incident electrons. The reason that the photoelectric effect is evidence for the particle nature of light has to do with how materials absorb that light energy and then eject it in the form of electrons.

[#1055] The reverse effect of X–ray emission is
Correct Answer

(D) Photoelectric

Explanation

Solution: When fast moving electrons strike on high atomic weight substance, X – ray is produced. In contrast, Photoelectric effect takes place when radiation of sufficient frequency incident on the metal surface and electrons are emitted. Hence, X – ray is the inverse phenomenon of photoelectric effect.