Question
A postage stamp kept below a rectangular glass block of refractive index 1.5 when viewed from vertically above it, appears to be raised by 7.0 mm. calculate the thickness of the glass block.
✓
Answer
Refractive index of the glass block, $\mu g =1.5$
Shift in the image $=7 mm$ or $0.7 cm$
Thickness of glass block or real depth $=$ ?
Shift $=$ Real depth $\times\left(1-\frac{1}{\mu}\right)$
$0.7=R \times\left(1-\frac{1}{1.5}\right)$
$R=\frac{0.7 \times 1.5}{0.5}=2.1 cm$
Shift in the image $=7 mm$ or $0.7 cm$
Thickness of glass block or real depth $=$ ?
Shift $=$ Real depth $\times\left(1-\frac{1}{\mu}\right)$
$0.7=R \times\left(1-\frac{1}{1.5}\right)$
$R=\frac{0.7 \times 1.5}{0.5}=2.1 cm$
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