Question

1. Focal length of plane mirror is

a. At infinity

b. Zero

c. Negative

d. None of these

2. Image formed by plane mirror is

a. Real and erect

b. Real and inverted

c. Virtual and erect

d. Virtual and inverted

3. A concave mirror gives real, inverted and same size image if the object is placed

a. At F

b. At infinity

c. At C

d. Beyond C

4. Power of the lens is -40, its focal length is

a. 4m

b. -40m

c. -0.25m

d. -25m

5. A concave mirror gives virtual, refract and enlarged image of the object but image of smaller size than the size of the object is

a. At infinity

b. Between F and C

c. Between P and F

d. At E

6. In optics an object which has higher refractive index is called

a. Optically rarer

b. Optically denser

c. Optical density d. Refractive index

7. The optical phenomena, twinkling of stars, is due to

a. Atmospheric reflection

b. Total reflection

c. Atmospheric refraction.

d. Total refraction

8. Convex lens focus a real, point sized image at focus, the object is placed

a. At focus

b. Between F and 2F

c. At infinity

d. At 2F

9. The unit of power of lens is

a. Metre

b. Centimeter

c. Diopter

d. M-¹

10. The radius of curvature of a mirror is 20cm the focal length is

a. 20cm

b. 10cm

c. 40cm

d. 5cm​

Answer 1

Answer:

Use the mirror equation to deduce that:

(a) an object placed between f and 2f of a concave mirror produces a real image beyond 2f.

(b) a convex mirror always produces a virtual image independent of the location of the object.

(c) the virtual image produced by a convex mirror is always diminished in size and is located between the focus and the pole.

(d) an object placed between the pole and focus of a concave mirror produces a virtual and enlarged image.

[Note: This exercise helps you deduce algebraically properties of images that one obtains from explicit ray diagrams.]