Under the Cartesian sign convention the focal length of a concave mirror is negative, and the mirror formula is 1/v + 1/u = 1/f, so this Class 10 sheet opens with signs and the equation. Magnification is given as m = h′/h = −v/u.
Key Takeaways
Concave mirror focal length is negative by the Cartesian convention (Q1).
The mirror formula is 1/v + 1/u = 1/f (Q2).
Q4 records m = h′/h = −v/u.
Section A: Multiple Choice Questions (1 Mark Each)
Choose the correct option for each question.
1.Using the Cartesian sign convention, the focal length of a concave mirror is taken as
(a) negative(b) positive(c) zero(d) always equal to the radius of curvature
2.The mirror formula is
(a) 1/v + 1/u = 1/f(b) 1/v − 1/u = 1/f(c) v + u = f(d) v − u = f
3.The focal length of a mirror is half of its
(a) radius of curvature(b) diameter(c) height(d) width
4.The magnification produced by a spherical mirror is given by
(a) m = h′/h = −v/u(b) m = h/h′ = u/v(c) m = v × u(d) m = h′ × h
(a) virtual, erect and diminished(b) real and inverted(c) virtual and enlarged(d) real and enlarged
Section B: Short Answer Type Questions (2 Marks Each)
Show all steps clearly.
7.Write the mirror formula.
8.Write the lens formula.
9.What is the relation between the focal length and the radius of curvature of a mirror?
10.Define magnification.
11.Why is a concave mirror used as a shaving or make-up mirror?
12.What is the sign of the focal length of a concave lens?
13.What type of image does a convex lens form when the object is placed beyond 2F?
14.State two uses of a convex mirror.
Section C: Numericals & Word Problems (3 Marks Each)
Apply the concepts to solve the problems. Show all working.
15.A concave mirror has a radius of curvature of 20 cm. Using f = R ÷ 2, find its focal length.
16.An object is placed at 30 cm from a concave mirror of focal length 15 cm. Using 1/v = 1/f − 1/u with the sign convention (u and f negative for a concave mirror), find the image distance.
17.An object is placed at 30 cm in front of a convex lens of focal length 10 cm. Using the lens formula 1/v = 1/f − 1/u with u = −30 cm and f = +10 cm, find the image distance.
18.A concave lens of focal length 20 cm has an object at 40 cm in front of it. Using the lens formula with f = −20 cm and u = −40 cm, find the image distance.
19.An object of height 5 cm produces an image of height 15 cm in a concave mirror. Using m = h′/h, find the magnification.
20.A convex mirror has a radius of curvature of 40 cm. Using f = R ÷ 2, find its focal length.
Answer Key
1. a) negative
2. a) 1/v + 1/u = 1/f
3. a) radius of curvature
4. a) m = h′/h = −v/u
5. a) converging lens
6. a) virtual, erect and diminished
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 is the sign of a concave mirror's focal length?
Negative by the Cartesian convention, option (a) in this worksheet (Q1).
What is the mirror formula?
1/v + 1/u = 1/f, option (a) in this worksheet (Q2).
How is magnification calculated?
m = h′/h = −v/u, option (a) in this worksheet (Q4).
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