WAEC - Physics (2001 - No. 23)
An incident ray is reflected normally by a plane mirror onto a screen where it forms a bright spot. The mirror and screen are parallel and 1m apart. If the mirror is rotated through 5o, calculate the displacement of the spot
8.7cm
10.0cm
15.4cm
17.6cm
คำอธิบาย
From the diagram above,
Tan\(\theta\) = \(\frac{\text{d}}{100}\)
Tan10º = \(\frac{\text{d}}{100}\)
d = 100 x Tan 10º = 100 x 0.1763 ≈ 17.6cm.