A point source emits unpolarized light uniformly in all directions. At two points A and B, the ratio of the intensities of light is 2. If a set of two polaroids having angle between their pass-axes is placed just before point B, then the new value of

Question

A point source $S$ emits unpolarized light uniformly in all directions. At two points A and B, the ratio $r = \frac{I_{A}}{I_{B}}$ of the intensities of light is 2. If a set of two polaroids having $45 °$ angle between their pass-axes is placed just before point B, then the new value of $r$ will be _______. [2024]

Smart Achievers · Accepted Answer

(8)

Using $r = \frac{I_{A}}{I_{B}}$

New intensity at B,

$I'_{B} = (\frac{I_{B}}{2}) \cos^{2} 45 ° = \frac{I_{B}}{4}$

New value of $r$ $= \frac{I_{A}}{I_{B}} = \frac{4 I_{A}}{I_{B}} = 4 \times 2 = 8$

Solution

Ans.
(8)

Using $I = I_{0} \cos^{2} θ$

New intensity at B,

$I'_{B} = (\frac{I_{B}}{2}) \cos^{2} 45 ° = \frac{I_{B}}{4}$

New value of $r$ $= \frac{I_{A}}{I_{B}} = \frac{4 I_{A}}{I_{B}} = 4 \times 2 = 8$

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Solution

Q. A point source S emits unpolarized light uniformly in all directions. At two points A and B, the ratio r=IAIB of the intensities of light is 2. If a set of two polaroids having 45° angle between their pass-axes is placed just before point B, then the new value of r will be _______. [2024]

Ans. (8) Using I=I0cos2θ New intensity at B, I'B=(IB2)cos245°=IB4 New value of r=IAIB=4IAIB=4×2=8

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Ans.
(8)

Using $I = I_{0} \cos^{2} θ$

New intensity at B,

$I'_{B} = (\frac{I_{B}}{2}) \cos^{2} 45 ° = \frac{I_{B}}{4}$

New value of $r$ $= \frac{I_{A}}{I_{B}} = \frac{4 I_{A}}{I_{B}} = 4 \times 2 = 8$