How much energy should be added to an electron to reduce its de-Broglie wavelength from ${10}^{-10}$ m to $0.5\times {10}^{-10}$m?
1. Four times the initial energy.
2. Thrice the initial energy.
3. Equal to the initial energy.
4. Twice the initial energy.

If the following particles are moving at the same velocity, then which among them will have the maximum de-Broglie wavelength?
1. Neutron               

2. Proton

3. $\mathrm{\beta }$-particle             

4. $\mathrm{\alpha }$-particle

The de-Broglie wavelength of a particle moving with a velocity $2.25\times {10}^8$ m/s is equal to the wavelength of the photon. What is the ratio of the kinetic energy of the particle to the energy of the photon? (velocity of light is $3\times {10}^8$ m/s)

A proton and an $\mathrm{\alpha }$-particle are accelerated through a potential difference of 100 V. What is the ratio of the wavelength associated with the proton to that of the alpha-particle?
1. $\sqrt{2}:1$              

2. 2:1

3. $2\sqrt{2}:1$             

4. $\frac{1}{2\sqrt{2}}:1$

What is the momentum of a photon in an X-ray beam of 10^-10 meter wavelength?

The energy of a quanta of frequency ${10}^{15}$ Hz and $\mathrm{h}=6.6\times {10}^{-34}\mathrm{ J}-\sec$ will be:

1. $6.6\times {10}^{-19}$ $\mathrm{J}$

$\mathrm{}$2.$6.6\times {10}^{-12}$ $\mathrm{J}$

3. $6.6\times {10}^{-49}$ $\mathrm{J}$

$\mathrm{}$4.$6.6\times {10}^{-41}$ $\mathrm{J}$

The number of photo-electrons emitted per second from a metal surface increases when:

A photon of energy 3.4 eV is incident on a metal having a work function of 2 eV. The maximum K.E. of photo-electrons is equal to:

The spectrum of radiation 1.0 x 10¹⁴ Hz is in the infrared region. The energy of one photon of this in joules will be:

1. $6.62\times {10}^{-48}$
2. $6.62\times {10}^{-20}$
3. $\frac{6.62}{3}\times {10}^{-28}$
4. $3\times 6.62\times {10}^{-28}$

A photocell is receiving light from a source placed at a distance of 1 m. If the same source is placed at a distance of 2 m, then the ejected electron: