In a photoelectric effect measurement, the stopping potential for a given metal is found to be V volt when radiation ofwavelength λ₀ is used. If radiation of wavelength 2λ₀ is used with the same metal then the stopping potential (in volt) will be

• $\frac{{\mathrm{V}}_0}{2}$

• 2V₀

• ${\mathrm{V}}_0 + \frac{\mathrm{hc}}{2 {\mathrm{e\lambda }}_0}$

• ${\mathrm{V}}_0 - \frac{\mathrm{hc}}{2 {\mathrm{e\lambda }}_0}$

32.

The wavelength of a 1 keV photon is 1.24 nm. The frequency of 1 MeV photon is

• 1.24 × 10¹⁵ Hz

• 2.4 × 10²⁰ Hz

• 1.24 × 10¹⁸ Hz

• 2.4 × 10²⁴ Hz

A photon of energy 8 eV is incident on metal surface of threshold frequency 1.6 x 10¹⁵ Hz. The kinetic energy of the photoelectrons emitted (in eV) : (Take h = 6 x 10^-34 J-s)

• 1.6

• 6

• 2

• 1.2

The rest mass of photon is

• $\frac{\mathrm{hv}}{\mathrm{c}}$

• $\frac{\mathrm{hv}}{{\mathrm{c}}^2}$

• $\frac{\mathrm{hc}}{\mathrm{\lambda }}$

• zero

If the wavelength of incident light changes from 400 nm to 300 nm, the stopping potential for photoelectrons emitted from a surface becomes approximately

• 1.0 V greater

• 1.0 V smaller

• 0.5 V greater

• 0.5 V smaller

A radio transmitter radiates 1 kW power at a wavelength 198.6 m. How many photons does it emit per second ?

• 10¹⁰

• 10²⁰

• 10³⁰

• 10⁴⁰

If the speed of light were 2/3 of its present value, the energy released in a given atomic explosion would

• decrease by a factor 2/3

• decrease by a factor 4/9

• decrease by a factor 5/9

• decrease by a factor $5\sqrt{9}$

The rate of emission of a black body at 0°C is R, its rate of emission at 273°C is

• 4 R

• 8 R

• 16 R

• 32 R

There are n₁ photons of frequency v₁ in a beam oflight. In an equally energetic beam there are n₂ photons of frequency v₂. Then the correct relation

• $\frac{{\mathrm{n}}_1}{{\mathrm{n}}_2} = \frac{{\mathrm{v}}_1}{{\mathrm{v}}_2}$

• $\frac{{\mathrm{n}}_1}{{\mathrm{n}}_2} = 1$

• $\frac{{\mathrm{n}}_1}{{\mathrm{n}}_2} = \frac{{\mathrm{v}}_2}{{\mathrm{v}}_1}$

• $\frac{{\mathrm{n}}_1}{{\mathrm{n}}_2} = \frac{{{\mathrm{v}}_2}^2}{{{\mathrm{v}}_1}^2}$

In photoelectric effect, the number of electrons ejected per second is

• proportional to the wavelength of light

• proportional to the intensity of light

• proportional to the work function of the metal

• proportional to the frequency of light