A concave mirror forms the image of an object on a screen.If the lower half of the mirror is covered with an opaque card, the effect would be to make the

image less bright.
lower half of the image disappear.
upper half of the image disappear.
image blurred.

Solution

Due to covering the reflection from lower part is not there so it makes the image less bright.

A diver inside water sees the setting sun at

41° to the horizon
49° to the horizon
0° to the horizon
45° to the horizon

A paper, with two marks having separation d, is held normal to the line of sight of an observer at a distance of 50m. The diameter of the eye-lens of the observer is 2 mm. Which of the following is the least value of d,so that the marks can be seen as separate ? (The mean wavelength of visible light may betaken as 5000 Å)

1.25 m
12.5 cm
1.25 cm
2.5 mm

Solution

An object is placed upright on the axis of a thin convex lens at a distance of four focal lengths (4f) from the center of the lens. An inverted image appears at a distance of 4/3 f on the other side of the lens. What is the ratio of the height of he image of the height of the object?

Solution

The ratio of object to image distance equals the ratio of object to image height. The ratio of image to object height is found by rearranging the ratios to give 4f /(4/3)f= 1/3.The image is demagnified by a factor of 3. Thus, answer choice A is the best answer.

An object is moved along the principal axis of a converging lens from a position 5 focal lengths from the lens to a position that is 2 focal lengths from the lens. Which statement about the resulting image is most accurate?

The image increases in size and decreases in distance from the lens
The image increases in size and increases in distance from the lens
The image decreases in size and decreases in distance from the lens
The image decreases in size and increases in distance from the lens

Solution

The easiest way to answer this question is with a fast sketch. Fora given object’s position, draw two rays from the top of the object. One ray is parallel to the principal axis and passes through the focal point on the opposite side of the lens. The other ray passes through the center of the lens. The top of the image appears where these two rays intersect.

Change the object’s position and repeat the process.You will observe that as the object approaches the lens while remaining beyond the focal length, the image produced on the opposite side of the lens moves away from the lens and increases in size.As an aside,the image is real and inverted.

A lens produces an image of an object on a screen. If a slab of refractive index n is placed in between lens and screen,the screen has to be moved by distance d behind. The thickness of slab is

nd
\(\frac{n-1}{nd}\)
\(\frac{(n-1)d}{n}\)
\(\frac{(n-1)d}{n}\)

Solution

Spherical aberration in a thin lens can be reduced by

using a monochromatic light
using a doublet combination
using a circular annular mark over the lens
increasing the size of the lens

Solution

Spherical abberation occurs due to the inability of a lens to coverage marginal rays of the same wave length to the focus as it converges the paraxial rays, This defect can be removed by blocking marginal rays. This can be done by using a circular annular mask over the lens.

Astronauts look down on earth surface from a space ship parked at an altitude of 500 km. They can resolve objects of the earth of the size (It can be assumed that the pupils diameter is 5mm and wavelength of light is 500 nm)

0.5 m
5 m
50 m
500 m

Solution

A pencil of light rays falls on a plane mirror and form a real image,so the incident rays are

parallel
diverging
converging
statement is false

Solution

When a object is real plane mirror form a virtual image and when object is virtual image will be real. Thus in this question object is virtual. Virtual object means object is at infinity. So rays(incident) converge on the mirror.

When white light enters a prism, its gets split into its constituent colours. This is due to

high density of prism material
because m is different for different wavelength
diffraction of light
velocity changes for different frequency

Solution

UnAttempted

0

Attempted

0

Correct

0

Wrong

0

Complete