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Practice MCQ Questions and answers on Physics-GK

Learn and practice General Knowledge questions and answers on Physics with very easy and understandable explanations. GK questions are very helpful different type of competitive exams. Page-4 section-13

Each section contains 100 MCQs on Physics .
31
The energy of a photon, whose momentum is 10 MeV/c, where c is the speed of light, is given by
Discuss
Answer & Solution
Answer: Option A
Solution:
A photon’s relativistic momentum is given by the equation,E = pc where p is the momentum.
P = 10 MeV/c
So, E = 10 MeV
32
The energy of a photon varies directly with its
Discuss
Answer & Solution
Answer: Option B
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.
33
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?
Discuss
Answer & Solution
Answer: Option C
Solution:
The speed of all the electromagnetic radiation are always same and equal to the numerical value 3 x 108 m/sec.
34
The threshold frequency is the frequency below which :
Discuss
Answer & Solution
Answer: Option C
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.
35
Which of the following supports particle nature of photons ?
Discuss
Answer & Solution
Answer: Option C
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.
36
The reverse effect of X–ray emission is
Discuss
Answer & Solution
Answer: Option D
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.
37
The term photon refers to
Discuss
Answer & Solution
Answer: Option B
Solution:
The term photon refers to sub atomic particle.
38
In a conductor
Discuss
Answer & Solution
Answer: Option D
Solution:
In a conductor the the valence band and the conduction band overlap each other.
39
The unit of intensity of electric field is
Discuss
Answer & Solution
Answer: Option A
Solution:
When considered in SI units the units of electric field intensity are Newton per coulombs. The electric field intensity is independent of the amount of charge on the test charge particle. It is measured the same all around the source charge regardless of the charge of the test charge particle.
40
. . . . . . . . . exerts a force on anything that has an electric charge.
Discuss
Answer & Solution
Answer: Option A
Solution:
Electric field exerts a force on anything that has an electric charge.