The de Broglie wavelength of an electron in the nth Bohr orbit is related to the radius R of the orbit as

1.  $\mathrm{n} \mathrm{\lambda }=\mathrm{nR}$

2.  $\mathrm{n} \mathrm{\lambda }=3/2 \mathrm{\pi } \mathrm{R}$

3.  $\mathrm{n} \mathrm{\lambda }=2 \mathrm{\pi } \mathrm{R}$

4.  $\mathrm{n} \mathrm{\lambda }=4 \mathrm{\pi } \mathrm{R}$

 

If the threshold wavelength for a photosensitive plate is \(4000\) Å, what will be the value of saturation current if radiation of wavelength \(5000\) Å is incident?
1. zero
2. \(1\) mA
3. \(3\) mA
4. data is insufficient to predict

The ratio of the de-Broglie wavelength of molecules of hydrogen and helium kept in two jars separately at temperatures of 27$°$C and 127$°$C respectively is:-

1.  $\sqrt{\frac{1}{2}}$

2.  $\sqrt{\frac{8}{3}}$

3.  $\frac{4}{3}$

4.  $\frac{3}{4}$

Light of two different frequencies whose photons have energies 1eV and 2.5eV respectively, successively illuminate a metal whose work function is 0.5 eV. The ratio of the maximum speeds of the emitted electrons will be

1.  1:5

2.  1:4

3.  1:2

4.  1:1

Assertion : Photosensitivity of a metal is high if its work function is small.
Reason : Work function = ${\mathrm{hf}}_0$ where ${\mathrm{f}}_0$ is the threshold frequency

A particle of mass 3m at rest decays into two particles of masses m and 2m having non-zero velocities. The ratio of the de-Broglie wavelengths of the particles $({\mathrm{\lambda }}_1/{\mathrm{\lambda }}_2)$ is

1. 1/2

2. 1/4

3. 2

4. None of these

When photons of energy hn fall on an aluminium plate (of work function ${\mathrm{E}}_0$), photoelectron on maximum kinetic energy K are ejected. If the frequency of the radiation is doubled, the maximum kinetic energy of the ejected photoelectron will be:-

1. K + ${\mathrm{E}}_0$

2. 2K

3. K

4. K + hn

In a photoelectric effect experiment

1. On increasing intensity and keeping frequency fixed the saturation current decreases

2. On increasing intensity and keeping frequency fixed the saturation current remains constant.

3. On increasing intensity, saturation current may increase.

4. On increasing, frequency saturation current may increase.