Question

The energy associated with a monochromatic ultraviolet radiation with a wave length of 10${}^{-3}$ m is?

• A. 19.86 $\times$ 10${}^{-23}$ J
• B. 19.86 $\times$ 10${}^{-22}$ J
• C. 19.86 $\times$ 10${}^{-20}$ J
• D. 19.86 $\times$ 10${}^{-21}$ J

Answer 1

Answer: (A)

19.86 $\times$ 10${}^{-23}$ J

v = $\frac{c}{\lambda }$ = $\frac{3\times {10}^8}{{10}^{-3}}$ = 3 $\times$ 10${}^{11}$ s${}^{-1}$
E = hv = 6.62 $\times$ 10$-34$ J s $\times$ 3 $\times$ 10${}^{11}$ = 19.86 $\times$ 10${}^{-23}$ J