Why does a smooth, polished surface look like a mirror but a sheet of paper does not — even though BOTH obey the laws of reflection?
AOn a polished surface, parallel incident rays remain parallel after reflection (regular reflection); on rough paper, parallel rays reflect in different directions (diffused reflection)
BThe paper has different laws of reflection
CSmooth surfaces obey different optics
DPaper does not reflect light at all
Answer & Solution
Correct answer: A. On a polished surface, parallel incident rays remain parallel after reflection (regular reflection); on rough paper, parallel rays reflect in different directions (diffused reflection)
At each point on the paper the laws of reflection are still obeyed; but the surface is microscopically irregular, so the normals at different points face in different directions. Parallel rays therefore scatter off in many directions (diffused reflection). On polished metal/glass the surface is uniform, normals are parallel, so reflected rays stay parallel — that's regular reflection, which forms a clear image.
Related questions
For a concave mirror, as an object moves from infinity towards the focus, the real imageThe power of a lens is −2.5 D. The lens isA small bulb is placed at the focus of a concave mirror of focal length 12 cm. The reflectWhich mirror is used as a rear-view mirror in vehicles, and why?An object 4 cm tall is placed 15 cm from a convex lens of focal length 10 cm. The image heA ray of light travelling in air enters water (n = 4/3). It bendsThe laws of reflection hold good forA convex lens forms a real image three times the size of the object on a screen. If the fo