Modern Physics CDS Questions

CDS Physics

Modern Physics MCQ Questions


1.
The photoelectric effect refers to the phenomenon in which:
A.
Electrons are emitted from the surface of a metal when light of sufficiently high frequency falls upon it
B.
Light is completely absorbed by a metal surface with no emission of any kind
C.
Electrons are absorbed into a metal surface upon exposure to light
D.
A metal surface emits light spontaneously without any external illumination
😑 View Answer Rough Work Error
ANSWER :
A. Electrons are emitted from the surface of a metal when light of sufficiently high frequency falls upon it
2.
Albert Einstein's explanation of the photoelectric effect, for which he was awarded the Nobel Prize in Physics, was based on which key concept proposed by Max Planck?
A.
The quantum (particle) nature of light, with light energy existing in discrete packets called photons
B.
The purely continuous wave nature of light, with no particle-like properties
C.
The theory of relativity, applied directly to the motion of electrons
D.
The complete absence of any energy associated with light
😑 View Answer Rough Work Error
ANSWER :
A. The quantum (particle) nature of light, with light energy existing in discrete packets called photons
3.
Einstein's Photoelectric Equation, describing the maximum kinetic energy of emitted photoelectrons, is given by:
A.
KE_max = φ - hf
B.
KE_max = h/f - φ
C.
KE_max = hf + φ
D.
KE_max = hf - φ (where φ is the work function of the metal)
😑 View Answer Rough Work Error
ANSWER :
D. KE_max = hf - φ (where φ is the work function of the metal)
4.
The 'work function' of a metal, relevant to the photoelectric effect, is defined as:
A.
The electrical resistance of the metal at room temperature
B.
The total kinetic energy of all electrons within the metal
C.
The minimum energy required to remove an electron from the surface of the metal
D.
The maximum possible frequency of light that the metal can absorb
😑 View Answer Rough Work Error
ANSWER :
C. The minimum energy required to remove an electron from the surface of the metal
5.
The 'threshold frequency' for a given metal, in the context of the photoelectric effect, refers to:
A.
The frequency at which a metal melts completely
B.
The maximum possible frequency of light that can ever be produced
C.
The minimum frequency of incident light below which no photoelectric emission can occur, regardless of light intensity
D.
The frequency of light required to produce the maximum possible current, irrespective of any other factor
😑 View Answer Rough Work Error
ANSWER :
C. The minimum frequency of incident light below which no photoelectric emission can occur, regardless of light intensity
6.
According to the experimentally observed characteristics of the photoelectric effect, increasing the INTENSITY of incident light (while keeping its frequency constant and above the threshold) results in:
A.
An increase in the maximum kinetic energy of the emitted photoelectrons, with no change in their number
B.
An increase in the number of photoelectrons emitted per second (and hence photoelectric current), but no change in their maximum kinetic energy
C.
No emission of photoelectrons whatsoever, regardless of intensity
D.
A decrease in the number of photoelectrons emitted
😑 View Answer Rough Work Error
ANSWER :
B. An increase in the number of photoelectrons emitted per second (and hence photoelectric current), but no change in their maximum kinetic energy