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

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

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

The stopping potential applied between a photocathode and respective anode is such that the fastest electron can fly only one half of the distance L between cathode and anode. For the same stopping potential, the distance between cathode and anode is reduced to L/2. The fastest electron can:

1.  reach the anode

2.  fly a distance greater than L/4

3.  fly a distance less than L/4

4.  fly a distance L/4

If the stationary proton and $\mathrm{\alpha }$-particle are accelerated through same potential difference, the ratio of de Broglie's wavelength will be

1.  $2$:1

2.  1:1

3.  $2\sqrt{2}$:1

4.  none of these