SATHEE: Optics Question 482

Optics Question 482

Question: A 60 watt bulb is hung over the center of a table 4 m x 4 m at a height of 3 m. The ratio of the intensities of illumination at a point on the centre of the edge and on the corner of the table is

[CPMT 1976, 84]

Options:

A) ${(17 / 13)}^{3 / 2}$

B) 2 / 1

C) 17 / 13

D) 5 / 4

Show Answer

Answer:

Correct Answer: A

Solution:

The illuminance at A is $I_{A} = \frac{L}{{(\sqrt{13})}^{2}} \times \cos θ_{1} = \frac{L}{13} \times \frac{3}{\sqrt{13}} = \frac{3 L}{{(13)}^{3 / 2}}$ .

The illuminance at B is $I_{B} = \frac{L}{{(\sqrt{17})}^{2}} \times \cos θ_{2}$

$= \frac{L}{17} \times \frac{3}{\sqrt{17}} = \frac{3 L}{{(17)}^{3 / 2}}$

$∴$ $\frac{I_{A}}{I_{B}} = {(\frac{17}{13})}^{3 / 2}$

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Optics Question 482

Question: A 60 watt bulb is hung over the center of a table 4 m x 4 m at a height of 3 m. The ratio of the intensities of illumination at a point on the centre of the edge and on the corner of the table is

Options:

Answer:

Solution:

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