MCQ
The work function for photoelectric effect:
  • A
    Is different for different metals.
  • B
    Is same for all metals.
  • C
    Depends upon the intensity of incident light.
  • D
    Depends upon the frequency of incident light.

Answer

  1. Is different for different metals.

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Free 238U nuclei kept in a train emit alpha particles. When the train is stationary and a uranium nucleus decays, a passenger measures that the separation between the alpha particle and the recoiling nucleus becomes x in time t after the decay. If a decay takes place when the train is moving at a uniform speed v, the distance between the alpha particle and the recoiling nucleus at a time t after the decay, as measured by the passenger will be:
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  2. x - vt
  3. x
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The electron emitted in beta radiation originates from:

A uniform wire of resistance R is uniformly compressed along its length, until its radius becomes n times the original radius.  Now resistance of the wire becomes

(a)   

(b)

(c)  

(d) nR

AB is a wire of uniform resistance. The galvanometer G shows no current when the length AC = 20cm and CB = 80 cm. The resistance R is equal to

(a) 2 Ω

(b) 8 Ω

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(d) 40 Ω

The resistance of a metal wire increases with increasing temperature on account of:

The work function for metals A, B and C are respectively 1.92 eV, 2.0 eV and 5 eV. According to Einstein’s equation, the metals which will emit photo electrons for a radiation of wavelength 4100 Å is/are

(a) None of these

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(c) A and B only

(d) All the three metals

In Young's interference experiment, the central bright fringe can be identified due to the fact that it:
A cylindrical tube, open at both ends, has a fundamental frequency v. The tube is dipped vertically in water so that half of its length is inside the water. The new fundamental frequency is:

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  2. $\frac{\text{v}}{2}$

  3. $\text{v}$

  4. $2\text{v}$

An object is placed first at infinity and then at 20 cm from the object side focal plane of the convex lens. The two images thus formed are 5 cm apart. The focal length of the lens is

(a) 5 cm  

(b) 10 cm

(c) 15 cm

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Which of these is a correct definition of electronic current?