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Solution - A 100 W Sodium Lamp Radiates Energy Uniformly in All Directions. the Lamp is Located at the Centre of a Large Sphere that Absorbs All the Sodium Light Which is Incident on It. the Wavelength of the Sodium Light is 589 Nm. (A) What is the Energy per Photon Associated with the Sodium Light? (B) at What Rate Are the Photons Delivered to the Sphere? - Particle Nature of Light: the Photon

ConceptParticle Nature of Light: the Photon

Question

A 100 W sodium lamp radiates energy uniformly in all directions. The lamp is located at the centre of a large sphere that absorbs all the sodium light which is incident on it. The wavelength of the sodium light is 589 nm. (a) What is the energy per photon associated with the sodium light? (b) At what rate are the photons delivered to the sphere?

Solution

Power of the sodium lamp, P = 100 W

Wavelength of the emitted sodium light, λ = 589 nm = 589 × 10−9 m

Planck’s constant, h = 6.626 × 10−34 Js

Speed of light, c = 3 × 108 m/s

(a)The energy per photon associated with the sodium light is given as:

E = hc/lambda

= (6.626 xx 10^(-34) xx 3 xx 10^8)/(589 xx 10^(-9)) = 3.37 xx 10^(-19) J

= (3.37 xx 10^(-19)) /1.6 xx 10^(-19) = 2.11 eV

(b)Number of photons delivered to the sphere = n

The equation for power can be written as:

P = nE

:. n = P/E

= 100/(3.37 xx 10^(-19)) = 2.96 xx  10^20 photons/s

Therefore, every second, 2.96 xx 10^20        photons are delivered to the sphere

Is there an error in this question or solution?

APPEARS IN

NCERT Physics Textbook for Class 12 Part 2
Chapter 11: Dual Nature of Radiation and Matter
Q: 7 | Page no. 407

Reference Material

Solution for question: A 100 W Sodium Lamp Radiates Energy Uniformly in All Directions. the Lamp is Located at the Centre of a Large Sphere that Absorbs All the Sodium Light Which is Incident on It. the Wavelength of the Sodium Light is 589 Nm. (A) What is the Energy per Photon Associated with the Sodium Light? (B) at What Rate Are the Photons Delivered to the Sphere? concept: Particle Nature of Light: the Photon. For the courses CBSE (Arts), CBSE (Commerce), CBSE (Science)
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