Test Index

JAMB Physics 2019 Paper

Question : 54

Total: 100

Solution:

Concept:

When a glass plate covers the mark, the apparent depth is reduced, causing the microscope to be raised by the apparent shift.

Explanation:

Real thickness of the glass plate:

t = 2\text{ cm}

Apparent shift:

d = 0.67\text{ cm}

The formula for apparent shift is

d = t\left(1 - \frac{1}{n}\right)

Substitute the values:

0.67 = 2\left(1 - \frac{1}{n}\right)

Divide both sides by 2:

0.335 = 1 - \frac{1}{n}

\frac{1}{n} = 1 - 0.335 = 0.665

Therefore

n = \frac{1}{0.665} = 1.5038 \approx 1.50

Answer:

The refractive index is

1.50

Correct option: A. 1.50.

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