Question

A tank is filled with water to a height of 12.5 cm. The apparent depth of a needle lying at the bottom of the tank is measured by a microscope to be 9.4 cm. What is the refractive index of water? If
water is replaced by a liquid of refractive index 1.63 up to the same height, by what distance would the microscope have to be moved to focus on the needle again?​

Answer 1

Explanation:

Find the moment of 25 N force about

point 'o'

( Refer the given fig.)

(1 Point)

3 m

O

25 N

8.33 Nm (clockwise)

75 Nm (clockwise)

8.33 Nm (anticlockwise)

75 Nm (anticlockwise)

Answer 2

Question:-

• A tank is filled with water to a height of 12.5 cm. The apparent depth of a needle lying at the bottom of the tank is measured by a microscope to be 9.4 cm. What is the refractive index of water? If water is replaced by a liquid of refractive index 1.63 up to the same height, by what distance would the microscope have to be moved to focus on the needle again?

To Find:-

• Find the distance would the microscope have to be moved to focus on the needle again?

Solution:-

Formula to be Used:-

• $\sf \: Apparent \: depth = \dfrac { Real \: depth } { μ }$

$\sf\dashrightarrow \: μ = \dfrac { Real \: depth } { Apparent \: depth }$

$\sf\dashrightarrow \: μ = \dfrac { 12.5 } { 9.4 }$

$\sf\dashrightarrow \: μ = 1.32$

• Refractive index is 1.32

Now ,

We have to find the Apparent depth:-

$\sf\dashrightarrow \: Depth = \dfrac { 12.5 } { 1.63 }$

$\sf\dashrightarrow \: Depth = 7.6$

• Depth of needle is 7.6

Now ,

We have to find the distance that the microscope should move:-

$\sf\dashrightarrow \: 9.4 - 7.6$

$\sf\dashrightarrow \: 1.8$

Hence ,

• We have to move 1.8 cm upwards to focus on needle again.