A plane mirror forms a virtual and erect image, and the power of a lens is measured in dioptres, so this Class 10 sheet opens with the mirror image and the lens unit. Refractive index is recorded as the vacuum-to-medium speed ratio for light.
Key Takeaways
A plane mirror image is virtual and erect (Q1).
The SI unit of lens power is the dioptre (Q2).
Q4 records refractive index as a ratio of light speeds.
Section A: Multiple Choice Questions (1 Mark Each)
Choose the correct option for each question.
1.The image formed by a plane mirror is
(a) real and inverted(b) virtual and erect(c) real and erect(d) virtual and inverted
4.The refractive index of a medium is defined as the ratio of the
(a) speed of light in vacuum to the speed of light in the medium(b) speed of light in the medium to the speed in vacuum(c) frequency of light in the two media(d) wavelength of light in the two media
5.The centre of curvature of a spherical mirror is
(a) the pole of the mirror(b) the centre of the sphere of which the mirror is a part(c) the midpoint of the mirror(d) the focus of the mirror
6.When a ray of light travels from a denser medium into a rarer medium at the critical angle, it
(a) refracts along the normal(b) reflects back into the denser medium(c) grazes along the surface of separation(d) bends towards the normal
Section B: Short Answer Type Questions (2 Marks Each)
Show all steps clearly.
7.State the two laws of reflection of light.
8.Define the focal length of a spherical mirror. State its relation with the radius of curvature.
9.Define the power of a lens and state its SI unit.
10.Define the refractive index of a medium.
11.Why does a ray of light bend towards the normal when it enters a denser medium from a rarer medium?
12.What is total internal reflection? State one condition for it to occur.
13.State Snell's law of refraction.
14.Why is a convex lens also called a converging lens?
Section C: Numericals & Word Problems (3 Marks Each)
Apply the concepts to solve the problems. Show all working.
15.A concave mirror has a focal length of 10 cm. Find its radius of curvature. (R = 2f)
16.An object is placed at a distance of 30 cm in front of a concave mirror of focal length 15 cm. Find the position of the image. (Use the mirror formula 1/v + 1/u = 1/f with the Cartesian sign convention, u = -30 cm and f = -15 cm)
17.An object is placed 30 cm from a convex lens of focal length 20 cm. Find the image distance. (Use the lens formula 1/v - 1/u = 1/f with the sign convention, u = -30 cm and f = +20 cm)
18.An object is placed 30 cm from a concave lens of focal length 15 cm. Find the position and nature of the image. (Use the lens formula with u = -30 cm and f = -15 cm)
19.The speed of light in glass is 2 × 10⁸ m/s. Find the refractive index of glass. (Speed of light in vacuum = 3 × 10⁸ m/s, n = c ÷ v)
20.A ray of light enters water of refractive index 4/3 from air. Find the speed of light in water. (Speed of light in vacuum = 3 × 10⁸ m/s, v = c ÷ n)
Answer Key
1. b) virtual and erect
2. b) dioptre
3. b) always positive
4. a) speed of light in vacuum to the speed of light in the medium
5. b) the centre of the sphere of which the mirror is a part
6. c) grazes along the surface of separation
7. Refer to solution guide.
8. Refer to solution guide.
9. Refer to solution guide.
10. Refer to solution guide.
11. Refer to solution guide.
12. Refer to solution guide.
13. Refer to solution guide.
14. Refer to solution guide.
15. Refer to solution guide.
16. Refer to solution guide.
17. Refer to solution guide.
18. Refer to solution guide.
19. Refer to solution guide.
20. Refer to solution guide.
End of Worksheet
People Also Ask
What image does a plane mirror form?
A virtual and erect image, option (b) in this worksheet (Q1).
What is the SI unit of power of a lens?
The dioptre, option (b) in this worksheet (Q2).
What is the refractive index?
The ratio of the speed of light in vacuum to its speed in the medium, option (a) in this worksheet (Q4).
Stuck on a similar problem? Clear your next doubt instantly with the Doubt Solver.
Browse more free worksheets for CBSE Grade 10.