Question

When the energy of the incident radiation is incredased by 20%, the kinetic energy of the photoelectrons emitted from a metal surface increased from 0.5 eV to 0.8 eV. The work function of the metal is:(a) 0.65 eV(b) 1.0 eV(c) 1.3 eV(d) 1.5 eV

Answer 1

Answer:

B) 1.0eV

Explanation:

Increased radiation = 20% (Given)

Kinetic energy change - 0.5~ 0.8 (Given)

Conservation of energy - hv = Ф0+1/2mv²max

= hv = hv0+1/2mv²max

= h (v-v0) = 1/2mv²max

Where h is the plank's constant, v is the frequency , v0 is the threshold frequency and Ф0 is the work function

Let work function is Ф

Initial energy of incidence = E

Kinetic energy = E-Ф = 0.5eV ---(1)

= 1.2E- Ф=0.8eV ---(2)

From (1) E=0.5eV+ Ф

= 1.2(0.5eV+ Ф) - Ф =0.8eV

= 0.6+0.2 Ф = 0.8eV

= Ф = 1eV

Thus, The work function of the metal is 1.0eV