SATHEE: Optics Question 172

Optics Question 172

Question: White light may be considered to be a mixture of waves with l ranging between $3900 A A$ and $7800 A A$ . An oil film of thickness $10, 000 A A$ is examined normally by reflected light. If m = 1.4, then the film appears bright for

Options:

A) $4308 A A, 5091 A A, 6222 A A$

B) $4000 A A, 5091 A A, 5600 A A$

C) $4667 A A, 6222 A A, 7000 A A$

D) $4000 A A, 4667 A A, 5600 A A, 7000 A A$

Show Answer

Answer:

Correct Answer: A

Solution:

The film appears bright when the path difference $(2 μ t \cos r)$ is equal to odd multiple of $\frac{λ}{2}$

i.e. $2 μ t \cos r = (2 n - 1) λ / 2$ where $n = 1, 2, 3 \dots . .$

$∴ λ = \frac{4 μ t \cos r}{(2 n - 1)}$

$= \frac{4 \times 1.4 \times 10, 000 \times 10^{- 10} \times \cos 0}{(2 n - 1)} = \frac{56000}{(2 n - 1)} A A$

$∴ λ = 56000 A A$

$18666 A A,$

$8000 A A,$

$6222 A A,$

$5091 A A,$

$4308 A A,$

$3733 A A .$ The wavelength which are not within specified range are to be refracted.

Optics Question 172

Question: White light may be considered to be a mixture of waves with l ranging between $3900 A A$ and $7800 A A$ . An oil film of thickness $10, 000 A A$ is examined normally by reflected light. If m = 1.4, then the film appears bright for

Options:

Answer:

Solution:

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Optics Question 172

Question: White light may be considered to be a mixture of waves with l ranging between 3900AA and 7800AA . An oil film of thickness 10,000AA is examined normally by reflected light. If m = 1.4, then the film appears bright for

Options:

Answer:

Solution:

Engineering Preparation

Medical Preparation

NCERT Books & Solutions

Important Resources

Other Resources

Syllabus

Test Platform

Sample Mock Test

Mentorship

NCERT Exercise Video Solution

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Question: White light may be considered to be a mixture of waves with l ranging between $3900 A A$ and $7800 A A$ . An oil film of thickness $10, 000 A A$ is examined normally by reflected light. If m = 1.4, then the film appears bright for