Account
It's free!

Share

Books Shortlist

# Solution for Monochromatic Radiation of Wavelength 640.2 Nm (1nm = 10−9 M) from a Neon Lamp Irradiates Photosensitive Material Made of Caesium on Tungsten Predict the New Stopping Voltage. - CBSE (Science) Class 12 - Physics

ConceptExperimental Study of Photoelectric Effect

#### Question

Monochromatic radiation of wavelength 640.2 nm (1nm = 10−9 m) from a neon lamp irradiates photosensitive material made of caesium on tungsten. The stopping voltage is measured to be 0.54 V. The source is replaced by an iron source and its 427.2 nm line irradiates the same photo-cell. Predict the new stopping voltage.

#### Solution

Wavelength of the monochromatic radiation, λ = 640.2 nm

= 640.2 × 10−9 m

Stopping potential of the neon lamp, V0 = 0.54 V

Charge on an electron, e = 1.6 × 10−19 C

Planck’s constant, h = 6.6 × 10−34 Js

Let phi_0 be the work function and ν be the frequency of emitted light.

We have the photo-energy relation from the photoelectric effect as:

eV0 = hν − phi_0

phi_0 = "hc"/lambda - eV_0

= (6.6 xx 10^(-34) xx 3 xx 10^8)/(640.2 xx 10^(-9)) - 1.6 xx 10^(-19) xx 0.54

= 3.093 xx 10^(-19) - 0.864 xx 10^(-19)

= 2.229 xx 10^(-19) J

= (2.229 xx 10^(-19))/(1.6  xx 10^(-19)) = 1.39 eV

Wavelength of the radiation emitted from an iron source, λ' = 427.2 nm

427.2 × 10−9 m

Let V'_0be the new stopping potential. Hence, photo-energy is given as:

eV_0^' = hc/lambda' - phio_0

= (6.6 xx 10^(-34) xx 3 xx 10^(8))/(427.2 xx 10^(-9)) - 2.229 xx 10^(-19)

= 4.63 xx 10^(-19) - 2.229 xx 10^(-19)

= 2.401 xx 10^(-19) J

= (2.401 xx 10^(-19))/(1.6 xx 10^(-19)) = 1.5 eV

Hence, the new stopping potential is 1.50 eV.

Is there an error in this question or solution?

#### APPEARS IN

NCERT Physics Textbook for Class 12 Part 2 (with solutions)
Chapter 11: Dual Nature of Radiation and Matter
Q: 27 | Page no. 410
Solution for question: Monochromatic Radiation of Wavelength 640.2 Nm (1nm = 10−9 M) from a Neon Lamp Irradiates Photosensitive Material Made of Caesium on Tungsten Predict the New Stopping Voltage. concept: Experimental Study of Photoelectric Effect. For the course CBSE (Science)
S