An \(\alpha -\) particle moves in a circular path of radius 0.83 cm in the presence of a magnetic field of \(0.25 \mathrm{~Wb} / \mathrm{m}^2\). The de-Broglie wavelength associated with the particle will be:

1.	\(1~\mathring {\text{A}}\)	2.	\(0.1~\mathring {\text{A}}\)
3.	\(10~\mathring {\text{A}}\)	4.	\(0.01~\mathring {\text{A}}\)

If the momentum of an electron is changed by p, then the de-Broglie wavelength associated with it changes by 0.5%. What is the initial momentum of the electron?

1. 200p

2. 400p

3. $\frac{\mathrm{p}}{200}$

4. 100p

In the Davisson and Germer experiment, the velocity of electrons emitted from the electron gun can be increased by

1. increasing the filament current

2. decreasing the filament current

3. decreasing the potential difference between the anode and filament

4. increasing the potential difference  between the anode and filament

A radioactive nucleus of mass M emits a photon

of frequency $\nu$ and the nucleus recoils. The recoil

energy will be:

(1) ${\mathrm{h}}^2{\mathrm{\nu }}^2/2 {\mathrm{Mc}}^2$

(2) zero

(3) h$\nu$

(4) ${\mathrm{Mc}}^2-\mathrm{h\nu }$

Photoelectric emission occurs only when the incident light has more than a certain minimum 

1. wavelength

2. intensity

3. frequency

4. power

The threshold frequency for a photo-sensitive metal is $3.3\times {10}^{14} \mathrm{Hz}.$ If the light of frequency $8.2\times {10}^{14} \mathrm{Hz}$ is incident on this metal, the cut-off voltage for the photo-electric emission is nearly:

1. 2 V                                        2. 3 V

3. 5 V                                         4. 1 V

The potential difference that must be applied to stop the fastest photoelectrons emitted by a nickel surface having a work function of 5.01 eV when ultraviolet light of 200 nm falls on it is:

When monochromatic radiation of intensity I falls on a metal surface, the number of photoelectrons and their maximum kinetic energy are N and T respectively. If the intensity of radiation is 2I what is the number of emitted electrons and their maximum kinetic energy?

The figure shows a plot of photo current versus anode potential for a photo sensitive surface for three difference radiations. Which one of the following is a correct statement?

(1) Curves a and b represent incident radiations of different frequencies and different intensities

(2) Curves a and b represent incident radiations of same frequency but of different intensities 

(3) Curves b and c represent incident radiations of different frequencies and different intensities

(4) Curves b and c represent incident radiations of same frequency having same intensity 

A particle of mass 1 mg has the same wavelength as an electron moving with a velocity of $3\times {10}^6$ $m{s}^{-1}$. What will be the velocity of the particle? (mass of electrons = 9 . 1 × 10^{- 31} kg )