Putting the values in equation 1 we get
1.7 sin θ
i
= 1.5 * sin 90
o
θ
i
= sin
-1
(0.88)
Therefore, A is the correct answer option.
Question 15
A photon of frequency 350 GHz is incident on a metal surface. What is the energy of the
photon in eV? (Planck’s constant = 6.6 x 10
-34
Js)
A. 2.34 x 10
-3
eV
B. 1.24 x 10
-2
eV
C. 1.44 x 10
-3
eV
D. 3.46 x 10
-2
eV
E. 0.45 eV
Correct Answer: C
Explanation:
Energy possessed by a photon is given as
E = hv --------------- (1)
Frequency is given in GHz so, we need to convert it into Hz.
1 GHz = 10
9
Hz
350 GHz = 3.5 x 10
11
Hz
Putting the values in equation 1 we get
E = 6.6 x 10
-34
* 3.5 * 10
11
Or E = 2.31 x 10
-22
J
We need to convert energy in Joules into eV as given below
1.6 x 10
-19
J = 1 eV
1 J = 1 / (1.6 x 10
-19
) eV
Or 2.31 x 10
-22
J = 1.44 x 10
-3
eV
Therefore, a photon with frequency of 350 GHz has energy of 1.44 x 10
-3
eV. Hence, C is the correct
answer option.
