The near point of a hypermetropic person is \(75\) cm from the eye. What is the power of the lens required to enable the person to read clearly a book held at \(25\) cm from the eye?
1. \(+2.67\) D
2. \(-1.25\) D
3. \(-2.67\) D
4. \(+1.25\) D
In the diagram given below, plot of angle of deviation () versus angle of incidence (i) for a triangular prism is given. Then the angle of minimum deviation is-
1.
2.
3.
4.
Find the value of the angle of emergence from the prism given below for the incidence ray shown. The refractive index of the glass is \(\sqrt{3}\).
1. \(45^{\circ}\)
2. \(90^{\circ}\)
3. \(60^{\circ}\)
4. \(30^{\circ}\)
A lens of large focal length and large aperture is best suited as an objective of an astronomical telescope since:
1. | a large aperture contributes to the quality and visibility of the images. |
2. | a large area of the objective ensures better light-gathering power. |
3. | a large aperture provides a better resolution. |
4. | all of the above. |
A point object is placed at a distance of \(60~\text{cm}\) from a convex lens of focal length \(30~\text{cm}\). If a plane mirror were put perpendicular to the principal axis of the lens and at a distance of \(40~\text{cm}\) from it, the final image would be formed at a distance of:
1. | \(30~\text{cm}\) from the plane mirror, it would be a virtual image. |
2. | \(20~\text{cm}\) from the plane mirror, it would be a virtual image. |
3. | \(20~\text{cm}\) from the lens, it would be a real image. |
4. | \(30~\text{cm}\) from the lens, it would be a real image. |
The far point of a myopic person is \(80\) cm in front of the eye. What is the power of the lens required to enable him to see very distant objects clearly?
1. \(-1.25\) D
2. \(+1.25\) D
3. \(-2.12\) D
4. \(+2.12\) D
What focal length should the reading spectacles have for a person for whom the least distance of distinct vision is \(50~\text{cm}\)?
1. \(-50~\text{cm}\)
2. \(+50~\text{cm}\)
3. \(-60~\text{cm}\)
4. \(+60~\text{cm}\)
Find the position of the image formed by the lens combination in the given figure.
1. | Final image is formed 30 cm to the right of the third lens. |
2. | Final image is formed 20 cm to the left of the third lens. |
3. | Final image is formed 30 cm to the left of the third lens. |
4. | Final image is formed 20 cm to the right of the third lens. |
A convex lens has a \(20~\text{cm}\) focal length in air. What is the focal length in water? (Refractive index of air-water = \(1.33\), refractive index for air-glass = \(1.5\))
1. \(+72.72~\text{cm}\)
2. \(+78.2~\text{cm}\)
3. \(-72.72~\text{cm}\)
4. \(+70.2~\text{cm}\)
The radii of curvature of the faces of a double convex lens are \(10\) cm and \(15\) cm. Its focal length is \(12\) cm. What is the refractive index of glass?
1. \(1.3\)
2. \(1.2\)
3. \(1.5\)
4. \(1.4\)