Q29.If 2. 5 × 10−6 N average force is exerted by a light wave on a non-reflecting surface of 30 cm2 area during 40 min of time span, the energy flux of light just before it falls on the surface is _______ W cm−2. (Round off to the Nearest Integer), (Assume complete absorption and normal incidence conditions are there)
What This Question Tests
This question tests the relationship between average force exerted by light on a non-reflecting surface and the energy flux of the light, requiring understanding of radiation pressure and conversion of units.
Concepts Tested
Formulas Used
F = (I_avg * A) / c (for complete absorption)
I = Energy / (Area * Time)
📚 NCERT Sections This Tests
11.4 — Monochromatic Light Of Wavelength 632.8 Nm Is Produced By A
Physics Class 12 · Chapter 11
11.4 Monochromatic light of wavelength 632.8 nm is produced by a helium-neon laser. The power emitted is 9.42 mW. (a) Find the energy and momentum of each photon in the light beam, (b) How many photons per second, on the average, arrive at a target irradiated by this beam? (Assume the beam to have uniform cross-section which is less than the target area), and (c) How fast does a hydrogen atom have to travel in order to have the same momentum as that of the photon?
12.5 — A Hydrogen Atom Initially In The Ground Level Absorbs A Photon,
Physics Class 12 · Chapter 12
12.5 A hydrogen atom initially in the ground level absorbs a photon, which excites it to the n = 4 level. Determine the wavelength and frequency of photon.
11.6 — The Threshold Frequency For A Certain Metal Is 3.3 × 1014 Hz. If Light
Physics Class 12 · Chapter 11
11.6 The threshold frequency for a certain metal is 3.3 × 1014 Hz. If light of frequency 8.2 × 1014 Hz is incident on the metal, predict the cut- off voltage for the photoelectric emission.
📋 Question Details
- Chapter
- EM Waves
- Topic
- Radiation pressure and energy flux
- Year
- 2021
- Shift
- 17 Mar Shift 1
- Q Number
- Q29
- Type
- Numerical
- NCERT Ref
- Class 12 Physics Ch 8: EM Waves
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