1. An object at a distance of 30 cm from a concave mirror gets its image at the same point. The focal length of the mirror is ?

+15 cm

– 15 cm

30 cm

– 30 cm

Answer: – 15 cm

Explanation:


2. If an incident ray passes through the focus, the reflected ray will ?

pass through the centre of curvature

retrace its path

be parallel to the principal axis

pass through the pole

Answer: be parallel to the principal axis

Explanation:


3. The Angle of reflection is equal to the angle of incidence ?

Sometimes

Never

Under special conditions

Always

Answer: Always

Explanation:

In accordance with the first law of reflection, which states that the angle of reflection is equal to the angle of incidence.


4. Magnification produced by a rear-view mirror fitted in vehicles ?

is equal to one

is more than one

is less than one

can be more than or less than one depending upon the position of the object in front of it

Answer: Is less than one

Explanation:

The convex mirror forms virtual, erect and diminished image of the object. And rear view mirror also forms some type of image. Therefore, magnification (m) produced by a rear view mirror fitted in vehicles is less than one i.e. m < 1.


5. When object moves closer to a concave lens the image by it shift ?

first towards and then away from the lens

away from the lens on the other side of lens

away from the lens on the same side of object

toward the lens

Answer: toward the lens

Explanation:

When object infinity, image is formed at the focus of concave lens of object is moved towards lens, the image is also moved from its focus towards lens and its size increase.


6. The image formed by concave mirror is real, inverted and of the same size as that of the object. The position of object should be ?

between focus and centre of curvature

beyond centre of curvature

at the focus

at the centre of curvature

Answer: between focus and centre of curvature

Explanation:

When object lies at C of a concave mirror, image is also formed at ‘C’ and having same size real and inverted.


7. For a real object, which of the following can produce a real image ?

Convex mirror

Concave lens

Concave mirror

Plane mirror

Answer: Concave mirror

Explanation:

Only concave mirror can produces a real image for the any position of object between its focus and infinity.


8. The angle of incidence for a ray of light having 45° reflection angle is ?

90°

45°

30°

Answer: 45°

Explanation:

For reflecting surface ?i = ?r


9. In which of the following, the image of an object placed at infinity will be highly diminished and point sized ?

Convex lens only

Convex mirror only

Concave mirror, convex mirror, concave lens and convex lens

Concave mirror only

Answer: Concave mirror, convex mirror, concave lens and convex lens

Explanation:


10. The refractive index of a medium with respect to vacuum is ?

Equal to one

Always greater than one

Always less than one

none of the above

Answer: Always less than one

Explanation: