Linear Magnification

Q.

What is the formula for linear magnification for lens?

v = Image distance

u = Object distance

1. $\frac{-v}{u}$

2. $\frac{v}{u}$

3. $\frac{u}{v}$

4. $\frac{-u}{v}$

Q.

A lens forms the image of an object placed at a distance of 45 cm from it on a screen placed at a distance 90 cm on other side of it. (a) Name the kind of lens. (b) Find : (i) the focal length of lens, and (ii) the magnification of image.

Q.

Define the focus (or focal point) and focal length of a convex mirror.

Q. Draw a ray diagram for a compound microscope in normal adjustment and least distance of distinct vision

Q. The magnification of a convex lens is , when the object is placed between one of the focii and the optic centre of the lens.

1. positive
2. zero
3. infinite
4. negative

Q.

What do you understand by the term magnification ? Write expression for it for a lens, explaining the meaning of the symbols used.

Q. The magnifying power of a simple microscope can be increased, if we use eye-piece of focal length.

1. higher
2. smaller
3. infinite

Q.

A spherical mirror and a lens are immersed in water. Compare to the way they work in air, Which one do you expect will be more affected by water?

Q.

How could you find the focal length of a convex lens rapidly but approximately?

Q.

A concave lens forms an erect image of $\frac{1}{3}$rd size of the object which is placed at a distance 30 cm in front of the lens. Find :

(a) the position of image, and

(b) the focal length of the lens.

Q. A real image is cast by a lens. What can be said about the magnification produced by the lens?

1. Negative
2. Zero
3. Can’t say
4. Positive

Q. Convex lens has positive focal length and concave lens has a negative focal length.

1. True
2. False

Q. The near-point of a person suffering from hypermetropia is at 50 cm from his eye. What is the nature and power of the lens needed to correct this defect? (Assume that the near-point of the normal eye is 25 cm).

Q. The focal length of a lens is negative.What kind of lens it is?

1. Concave
2. Cannot be determined
3. Convex

Q.

Solve these numericals

c. If the sum of focal length and radius of curvature is $30cm$, what is the focal length of that spherical mirror?

Q.

What happens to the magnifying power of a microscope, when its length increases?

Q. A convex lens of focal 20 cm forms an image at a distance of 40 cm on the other side of the lens. Find the distance of the object from the lens. What is the magnification of the object? [4 MARKS]

Q.

What is the nature of a mirror having a focal length of $-15cm$?

Q.

With the help of a diagram, define the principal focus of

a. convex lens

Q. At what distance the object should be placed in front of a concave lens of focal length 20 cm so that the image will be formed at distance 10 cm from the lens? What is the magnification of the object?
[4 MARKS]

Q.

How does the eye lens change its focal length to see nearby objects?

Q. Radius of curvature of a concave lens is 60 cm. What is the focal length?

1. -30
2. -60
3. 60
4. 30

Q.

If the radius of curvature of a convex mirror is 36 cm, what is its focal length?

Q. The object and the image distances are 10 cm & 30 cm respectively for a lens. Image is formed on same side of the object then the focal length is .

1. $25cm$
2. $-10cm$
3. $+15cm$
4. $-15cm$

Q.

A divergence lens of focal length of 30cm forms the image of an object of size 6 cm on the same side as of the object at a distance of 15cm from its optical centre .use lens formula to determine the distance of the object from the lens and the size of image formed ...

Draw a ray daigram to show the formation of image in the above situation .

Q.

if a convergent beam of light passes through a diverging lens, the result

1. may be a converging beam

2. may be a diverging beam

3. may be a parallel beam

4. All of the above

Q.

A converging beam of solar rays is incident on a concave spherical mirror whose radius of curvature is $0.8$ m. Determine the position of the point on the principal axis of the mirror, where the reflected rays intersect, if the extensions of the incident rays intersect the principal axis $40$ cm from the mirrors pole?

1. $10$ cm from the pole

2. $30$ cm from the pole

3. $50$ cm from the pole

4. $20$ cm from the pole

Q. Choose the correct ray diagram for a magnifying mirror.

1. 
2. 
3. 
4. 

Q.

An object is placed at a distance at a distance of $10cm$ in front of a concave lens of focal length $10cm$. Find the linear magnification of the lens?

1. 1

2. $\frac{1}{3}$

3. $\frac{1}{2}$

4. $\frac{1}{4}$

Q. The maximum magnifying power of a convex lens of focal length 5 cm can be:

1. 1
2. 25
3. 6
4. 10