Question

The kinetic energy of an electron is E when the incident wavelength is λ. To increase the KE of the electron to 2E, the incident wavelength must be-

• A. 2λ
• B. λ/2
• C.
• D.

Answer 1

Answer: (C)

Answer 2

E = – φ ...(1)

2E = $\frac { \mathrm { hc } } { \lambda ^ { \prime } }$ – φ …(2)

after solving

λ' =