Q1.Power of a LensEasy · 1m
Find the power of a convex lens of focal length 50 cm.
Answer: P = 1/f (in metres) = 1/0.5 = +2 D.
Class 10 · Science · Important Questions
Light — Reflection and Refraction — Important Questions
Q2.Laws of ReflectionEasy · 2m
State the two laws of reflection of light.
Answer: (i) The angle of incidence is equal to the angle of reflection. (ii) The incident ray, the reflected ray and the normal at the point of incidence all lie in the same plane.
Q3.Convex MirrorMedium · 2m
Why is a convex mirror used as a rear-view mirror in vehicles?
Answer: It always forms an erect, virtual and diminished image and has a wider field of view, so the driver can see more traffic behind.
Q4.RefractionMedium · 2m
Why does a pencil appear bent when partly dipped in water?
Answer: Light from the submerged part bends (refracts) as it passes from water into air because its speed changes, so the pencil appears displaced and bent at the surface.
Q5.Mirror FormulaMedium · 3m
An object is placed 20 cm from a concave mirror of focal length 10 cm. Find the image distance.
Answer: Using 1/v + 1/u = 1/f with u = −20 cm and f = −10 cm: 1/v = 1/f − 1/u = −1/10 + 1/20 = −1/20 ⇒ v = −20 cm (real, inverted, same size).
More for this chapter
NCERT Solutions
Step-by-step chapter solutions
Revision Notes
Quick notes & key points
Formula Sheets
All formulas in one place
Search this topic
All content related to “Light — Reflection and Refraction”