(a) Define binding energy in an atom.
(b) List three evidence to support the claim that X-rays are electromagnetic waves.
(c) List three peaceful uses of nuclear energy.
(d) Light of wavelength 4.5 x 10\(^{-7}\) in is incident on a metal resulting in the emission of photo electrons. If the work function of the metal is 3.0 x 10\(^{-9}\) J, calculate the:
(i) frequency of the incident light;
(ii) energy of the incident light;
(iii) energy of the photoelectrons. [Speed of light = 3.0 x 10\(^8\) ms\(^{-1}\), h = 6.6 x 10\(^{-34}\) Js]
Explanation
(a) Binding energy is the minimum energy required to seperate the nucleus of an atom.
(b) Three evidences in support of the claim that x -rays are electromagnetic waves are:
(i) They can be polarized.
(ii) They can travel through a vacuum.
(iii) They travel with the speed of light.
(iv) They are not affected by electric field.
(v) They are not affected by magnetic field.
(c) Three peaceful uses of nuclear energy are:
(i) It is used in the treatment of tumour.
(ii) It is used to power submarines.
(iii) It is used to generate electricity.
(d) (1) c = f\(\lambda\) or f = \(\frac{c}{\lambda}\)
f = \(\frac{3.0 \times 10^8}{4.5 \times 10^{-7}}\)
f = 6.67 x10\(^{14}\)Hz
(ii) E = hf
= 6.67 x10\(^{-34}\) x 6.67 x10\(^{14}\)J
= 4.4 x10\(^{-19}\)J
(iii) K.E = E- W
= 4.4 x 10\(^{-19}\)
=1.4 x 10\(^{-19}\) - 3.0 x 10\(^{-19}\)
=1.4 x 10\(^{-19}\)J