Paraxial Approximation

Q. Which of the following (referred to a spherical mirror) do (does) not depend on whether the rays are paraxial or not?

1. Pole
2. Focus
3. Radius of curvature
4. Principal axis.

Q. A luminous point object is placed at $O$, whose image is formed at $I$ as shown in figure. Line $AB$ is the optical axis. Which of the following statement is/are correct?

1. If a lens is used to obtain the image, then it must be a diverging lens and its optical centre will be the intersection point of line $AB$ and $OI$.
2. If a lens is used to obtain the image, then it must be a converging lens and its optical centre will be the intersection point of line $AB$ and $OI$.
3. I is a real image.
4. If a mirror is used to obtain the image then the mirror must be concave and object and image subtend equal angles at the pole of the mirror.

Q. Since sun is faraway from the earth, the sun rays can be assumed parallel when they reach the earth surface.

1. True
2. False

Q. In image formation from spherical mirrors, only paraxial rays are considered because they

1. are easy to handle geometrically
2. are not parallel to principal axis
3. form nearly a point image of a point source
4. are far from principal axis

Q. Find the angle of incidence $\left(\theta \right)$ of a paraxial ray incident on a concave mirror of large aperture, for which it passes through the pole $\left(P\right)$ after reflection.

1. ${60}^{\circ }$
2. ${30}^{\circ }$
3. ${75}^{\circ }$
4. ${45}^{\circ }$

Q. A beam of parallel rays is incident on a concave mirror such that they make a very small angle $\theta$ with the principle axis of the concave mirror. The distance from the focus on the focal plane where rays converge after reflection is

1. $2f\theta$
2. $3f\theta$
3. $4f\theta$
4. $f\theta$

Q. In image formation from spherical mirrors, only paraxial rays are considered because they

1. are easy to handle geometrically
2. are not parallel to principal axis
3. form nearly a point image of a point source
4. are far from principal axis

Q. Which of the following statements are true regarding paraxial approximation?

1. The rays coming to the mirror must be parallel to the principal axis of the mirror
2. The rays falling on the spherical mirror must be extremely close to the principal axis of the mirror
3. Only the rays parallel to the principal axis of the spherical mirror should be used to draw the ray diagram
4. all of the above.

Q. Since sun is faraway from the earth, the sun rays can be assumed parallel when they reach the earth surface.

1. True
2. False

Q. Which of the following (referred to a spherical mirror) do (does) not depend on whether the rays are paraxial or not?

1. Pole
2. Focus
3. Radius of curvature
4. Principal axis.