# 38 Lecture

## Geometrical Optics

Geometrical optics is a branch of physics that deals with the study of light propagation through a medium using geometrical principles.

## Important Mcq's Midterm & Finalterm Prepration Past papers included

Which of the following laws states that the incident ray, the reflected ray, and the normal to the surface of reflection all lie in the same plane?

A) Law of reflection

B) Law of refraction

C) Principle of least time

D) Principle of rectilinear propagation

What is the angle of incidence for total internal reflection?

A) 0°

B) 90°

C) 180°

D) Greater than the critical angle

Answer: D) Greater than the critical angle

Which type of lens is thicker at the center than at the edges?

A) Convex lens

B) Concave lens

C) Plano-convex lens

D) Plano-concave lens

The focal length of a lens depends on which of the following?

A) The curvature of the lens

B) The refractive index of the lens

C) Both A and B

D) None of the above

Answer: C) Both A and B

Which of the following is a measure of the degree of bending of light as it passes from one medium to another?

A) Reflection coefficient

B) Refraction coefficient

C) Diffraction coefficient

D) Absorption coefficient

What is the angle of incidence for a light ray that undergoes minimum deviation while passing through a prism?

A) Greater than the critical angle

B) Equal to the critical angle

C) Less than the critical angle

D) Depends on the refractive index of the prism

Answer: B) Equal to the critical angle

Which of the following is a measure of the ability of a lens to focus light?

A) Focal length

B) Refractive index

C) Aberration

D) Dispersion

The ratio of the speed of light in a vacuum to the speed of light in a medium is known as which of the following?

A) Refractive index

B) Reflection coefficient

C) Absorption coefficient

D) Transmission coefficient

Which of the following occurs when light waves from different sources combine to form a pattern of constructive and destructive interference?

A) Diffraction

B) Reflection

C) Refraction

D) Interference

Which of the following is a measure of the degree of spreading of light as it passes through an aperture or around an obstacle?

A) Reflection

B) Refraction

C) Diffraction

D) Interference

## Subjective Short Notes Midterm & Finalterm Prepration Past papers included

What is the principle of rectilinear propagation?

Answer: The principle of rectilinear propagation states that light travels in a straight line in a homogeneous medium.

What is the law of refraction?

Answer: The law of refraction states that the ratio of the sine of the angle of incidence to the sine of the angle of refraction is constant and is known as the refractive index of the medium.

What is the principle of reflection?

Answer: The principle of reflection states that the angle of incidence is equal to the angle of reflection, and the reflected ray and the incident ray are on the same plane perpendicular to the reflecting surface.

What is the principle of least time?

Answer: The principle of least time states that light travels between two points in such a way that the time taken is minimized.

What is lens imaging?

Answer: Lens imaging is the process of forming images of objects by focusing the light rays that pass through lenses.

What is the difference between a virtual image and a real image?

Answer: A virtual image is an image that is formed by the apparent intersection of light rays that appear to come from the image location, while a real image is an image that is formed by the actual intersection of light rays that come from the image location.

What are optical aberrations?

Answer: Optical aberrations are deviations from ideal optical behavior, caused by factors such as lens imperfections, temperature changes, and atmospheric conditions.

What is spherical aberration?

Answer: Spherical aberration occurs when light rays passing through the edges of a lens are refracted differently from those passing through the center, causing the image formed to be blurred and distorted.

What is chromatic aberration?

Answer: Chromatic aberration is caused by the different refractive indices of different wavelengths of light, which results in color fringes around the edges of an image.

What is coma?

Answer: Coma occurs when light rays entering a lens at an angle are not focused on the same point as those entering at the center of the lens, causing the image to be distorted.

### Geometrical Optics

Geometrical optics is a branch of physics that deals with the study of light propagation through a medium using geometrical principles. This branch of optics is concerned with the behavior of light in relation to the boundaries of the medium it travels through, such as the boundaries between air and a solid object or between two different materials. The study of geometrical optics is useful in the design of optical instruments such as telescopes, cameras, and lenses. The principle of rectilinear propagation states that light travels in a straight line in a homogeneous medium. The speed of light is constant in a given medium and it changes when it passes through a different medium. This is referred to as the law of refraction, which states that the ratio of the sine of the angle of incidence to the sine of the angle of refraction is constant and is known as the refractive index of the medium. This principle is essential in understanding the behavior of light as it passes through different media. The principle of reflection states that when a ray of light hits a surface, it is reflected back in a predictable manner. The angle of incidence is equal to the angle of reflection, and the reflected ray and the incident ray are on the same plane perpendicular to the reflecting surface. The law of reflection is used in designing optical instruments such as mirrors. Another important principle in geometrical optics is the principle of least time, which states that light travels between two points in such a way that the time taken is minimized. This principle is used in designing lenses and mirrors, as it allows us to predict the path of light through these optical components. Geometrical optics is also concerned with the formation of images by lenses and mirrors. When a ray of light passes through a lens, it is refracted at the surface of the lens and the refracted ray changes direction. The degree of refraction depends on the curvature of the lens surface and the refractive index of the material of the lens. The combination of lenses can form images of objects by focusing the light rays that pass through them. This process is known as lens imaging and is used in designing cameras, telescopes, and other optical instruments. Mirrors also play an important role in image formation in geometrical optics. The reflection of light by a mirror produces an image that is virtual and appears to be behind the mirror. The size and orientation of the image depend on the angle of incidence of the light rays on the mirror surface. The concept of optical aberrations is also an important aspect of geometrical optics. These are deviations from ideal optical behavior, caused by factors such as lens imperfections, temperature changes, and atmospheric conditions. Some of the common types of aberrations include spherical aberration, chromatic aberration, and coma. Spherical aberration occurs when light rays passing through the edges of a lens are refracted differently from those passing through the center. This causes the image formed to be blurred and distorted. Chromatic aberration is caused by the different refractive indices of different wavelengths of light, which results in color fringes around the edges of an image. Coma occurs when light rays entering a lens at an angle are not focused on the same point as those entering at the center of the lens, causing the image to be distorted. In conclusion, geometrical optics is a fundamental branch of physics that deals with the propagation of light through different media using geometrical principles. The laws of reflection, refraction, and least time are important principles in this field, as they allow us to understand the behavior of light as it passes through different media. The formation of images by lenses and mirrors, and the concept of optical aberrations, are also important aspects of geometrical optics. The principles of geometrical optics are used in the design of a wide range of optical instruments, from simple mirrors and lenses to complex