Electromagnetic radiation and the photoelectric effect — practice questions

Question 1 · difficulty L2 · understanding

Consider two radiations of wavelengths $\lambda_1=2000\mathop {\rm{A}}\limits^{\rm{o}}$ $\lambda_2=6000 \mathop {\rm{A}}\limits^{\rm{o}}$ The ratio of the energies of these two radiations $\left(\frac{E_1}{E_2}\right)$ is $\_\_\_\_$ (Nearest integer).

Question 2 · difficulty L2 · understanding

The surface of sodium metal is irradiated with radiation of wavelength $x$ nm. The kinetic energy of ejected electrons is $2.8 \times 10^{-20}\ \text{J}$. The work function of sodium is $2.3$ eV. The value of $x$ is ________ $\times 10^2$ nm. (Nearest integer) (Given: $h=6.6 \times 10^{-34}\ \text{J s}$ ; $1\ \text{eV} = 1.6 \times 10^{-19}\ \text{J}$ ; $c = 3.0 \times 10^8\ \text{m s}^{-1}$)

Question 3 · difficulty L2 · understanding

A hypothetical electromagnetic wave is show below. The frequency of the wave is $$\mathrm{x} \times 10^{19} \mathrm{~Hz}$$. $$\mathrm{x}=$$ _________ (nearest integer)

Question 4 · difficulty L2 · understanding

The ionization energy of sodium in $$\mathrm{~kJ} \mathrm{~mol}^{-1}$$, if electromagnetic radiation of wavelength $$242 \mathrm{~nm}$$ is just sufficient to ionize sodium atom is _______.

Question 5 · difficulty L2 · understanding

Values of work function (W$$_0$$) for a few metals are given below Metal Li Na K Mg Cu Ag W$$_0$$/eV 2.42 2.3 2.25 3.7 4.8 4.3 The number of metals which will show photoelectric effect when light of wavelength $$400 \mathrm{~nm}$$ falls on it is ___________ Given: $$\mathrm{h}=6.6 \times 10^{-34} \mathrm{~J} \mathrm{~s}$$ $$c=3 \times 10^{8} \mathrm{~ms}^{-1}$$ $$e=1.6 \times 10^{-19} \mathrm{C}$$

Question 6 · difficulty L2 · understanding

The number of incorrect statement/s about the black body from the following is __________ (A) Emit or absorb energy in the form of electromagnetic radiation. (B) Frequency distribution of the emitted radiation depends on temperature. (C) At a given temperature, intensity vs frequency curve passes through a maximum value. (D) The maximum of the intensity vs frequency curve is at a higher frequency at higher temperature compared to that at lower temperature.

Question 7 · difficulty L2 · understanding

If the work function of a metal is 6.63 $$\times$$ 10 $$-$$19 J, the maximum wavelength of the photon required to remove a photoelectron from the metal is ____________ nm. (Nearest integer) [Given : h = 6.63 $$\times$$ 10 $$-$$34 J s, and c = 3 $$\times$$ 10 8 m s $$-$$1 ]

Question 8 · difficulty L2 · understanding

A 50 watt bulb emits monochromatic red light of wavelength of 795 nm. The number of photons emitted per second by the bulb is x $$\times$$ 10 20 . The value of x is __________. [Given : h = 6.63 $$\times$$ 10 $$-$$34 Js and c = 3.0 $$\times$$ 10 8 ms $$-$$1 ]

Question 9 · difficulty L2 · understanding

The number of photons emitted by a monochromatic (single frequency) infrared range finder of power 1 mW and wavelength of 1000 nm, in 0.1 second is x $$\times$$ 10 13 . The value of x is _____________. (Nearest integer) (h = 6.63 $$\times$$ 10 $$-$$34 Js, c = 3.00 $$\times$$ 10 8 ms $$-$$1 )

Question 10 · difficulty L2 · understanding

A metal surface is exposed to 500 nm radiation. The threshold frequency of the metal for photoelectric current is 4.3 $$\times$$ 10 14 Hz. The velocity of ejected electron is ____________ $$\times$$ 10 5 ms $$-$$1 (Nearest integer) [Use : h = 6.63 $$\times$$ 10 $$-$$34 Js, m e = 9.0 $$\times$$ 10 $$-$$31 kg]