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

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

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. ${\mathrm{Mc}}^2-\mathrm{h\nu }$

In photoelectric emission process from a metal of work function 1.8 eV, the kinetic energy of most energetic electrons is 0.5 eV. The corresponding stopping potential is

1. 1.2 V

2. 0.5 V

3. 2.3 V

4. 1.8 V

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

1. wavelength

2. intensity

3. frequency

4. power

Electrons used in an electron microscope are accelerated by a voltage of 25 kV. If the voltage is increased to 100 kV then the de-Broglie wavelength associated with the electrons would

1. decrease by 2 times

2. decrease by 4 times

3. increase by 4 times

4. increase by 2 times

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

A source S₁ is producing, 10¹⁵ photons/s of wavelength 5000 $\stackrel{\circ }{A}$. Another source S₂ is producing 1.02$\times$ 10¹⁵ photons per second of wavelength 5100 $\stackrel{\circ }{A}$. Then, (power of S₂)/(power of S₁) is equal to

1. 1.00                 2. 1.02

3. 1.04                 4. 0.98