Physics Chapter on Light

Questions and Answers

What is the primary reason we are able to see objects in our environment?

Light is reflected off objects to our eyes. (correct)

Objects emit light on their own.

Objects absorb all light that hits them.

Light passes through objects without interaction.

Which of the following describes the behavior of light as a wave?

Photoelectric effect.

Reflection.

Interference. (correct)

Absorption.

What is meant by the term 'wave-particle duality' in relation to light?

Light's behavior is inconsistent and unpredictable.

Light can only behave as a wave.

Light can only behave as a particle.

Light exhibits properties of both waves and particles. (correct)

What happens to light when it travels from one medium to another?

It can be reflected, refracted, or absorbed. Signup and view all the answers

What is the value of the speed of light in a vacuum, approximately?

3.0 × 10^8 m/s Signup and view all the answers

What defines a polished medium in relation to light reflection?

A medium that causes regular reflection due to a smooth surface. Signup and view all the answers

When light is incident on a plane mirror, what happens to most of it?

Most is reflected by the mirror. Signup and view all the answers

Which of the following statements about the laws of reflection is true?

The incident ray, reflected ray, and normal all lie in the same plane. Signup and view all the answers

What does the Law of Reflection state?

The angle of incidence is equal to the angle of reflection. Signup and view all the answers

What is the focal length of a spherical mirror related to its radius of curvature?

Focal length is half the radius of curvature. Signup and view all the answers

Which of the following accurately describes a concave mirror?

The light converges at a focal point located on the same side as the object. Signup and view all the answers

How does light behave in a homogeneous medium according to Fermat's Principle?

Light travels in straight lines. Signup and view all the answers

What type of image is formed by a plane mirror?

Virtual and erect Signup and view all the answers

What is the distance between the pole and the focus of a spherical mirror called?

Focal length Signup and view all the answers

What phenomenon describes the way light appears to be reflected on a hot road, creating a mirage?

Light following the quickest path as per Fermat’s Principle Signup and view all the answers

What happens to a ray that passes through the center of curvature upon striking a concave mirror?

It retraces its path back to the object. Signup and view all the answers

Which term refers to the midpoint of a spherical mirror?

Pole Signup and view all the answers

Which of the following statements is true regarding the characteristics of images?

Virtual images can only be erect. Signup and view all the answers

In the mirror formula, what does the variable 'u' represent?

Object distance Signup and view all the answers

Which one of the following statements reflects a common misconception about image formation by mirrors?

Images are always larger than the objects. Signup and view all the answers

What role does Fermat's Principle play in the rectilinear propagation of light?

It validates that light travels in straight lines in a homogeneous medium. Signup and view all the answers

What is the function of a convex mirror in daily life?

It allows for a wider field of view in rearview mirrors. Signup and view all the answers

Which of the following accurately describes the principal axis of a spherical mirror?

The line passing through the focus and the center of curvature. Signup and view all the answers

What is meant by a 'diminished' image?

An image that is smaller than the object. Signup and view all the answers

What type of lens diverges light rays that are parallel to its principal axis?

Concave lens Signup and view all the answers

Which formula represents the relationship between object distance, image distance, and focal length of a spherical lens?

1/v = 1/u = 1/f Signup and view all the answers

What is the SI unit of power of a lens?

Dioptre Signup and view all the answers

If an object is placed at 80 cm from a concave lens with a focal length of 20 cm, what will be the height of the image formed if the object height is 3 cm?

0.6 cm Signup and view all the answers

Calculate the refractive index of diamond with respect to carbon disulphide given their refractive indices as 2.42 and 1.63 respectively.

1.48 Signup and view all the answers

What does the refractive index of a medium represent?

The ratio of the speed of light in a vacuum to the speed of light in that medium Signup and view all the answers

What occurs during total internal reflection?

Light is completely reflected back into the denser medium when the incidence angle is greater than the critical angle Signup and view all the answers

What represents the critical angle in optical terms?

The minimum angle of incidence that results in total internal reflection Signup and view all the answers

What defines a convex lens?

A lens formed by binding two spherical surfaces, both curving outward Signup and view all the answers

What is the focal length of a lens?

The distance from the optical centre to the focus of the lens Signup and view all the answers

What happens when light passes through a concave lens?

It appears to diverge from a point on the same side as the incoming light Signup and view all the answers

What is the optical centre of a spherical lens?

The symmetric center of the lens where light is unaltered Signup and view all the answers

Which statement best describes the principle of refraction through curved surfaces?

Refraction at curved surfaces follows the standard laws of refraction Signup and view all the answers

Study Notes

Introduction to Light

Light is energy that allows visibility; it originates from a source and interacts with objects.
Electromagnetic waves travel at the speed of light, which is approximately 3.0 × 10^8 m/s.

Nature of Light

Exhibits properties of rays (reflection), waves (interference, diffraction), and particles (photoelectric effect).
Wave-particle duality explains light's behavior depending on the situation.

Laws of Reflection

When light hits a surface, it can be absorbed, reflected, or refracted.
Laws of reflection state that the incident ray, reflected ray, and normal lie in the same plane, and the angle of incidence equals the angle of reflection (∠i = ∠r).

Propagation of Light

Light travels in straight lines (rectilinear propagation).
Fermat’s Principle states that light takes the quickest path, which is not always the shortest.

Applications of Fermat’s Principle

In a uniform medium, light travels in straight lines, supporting the law of reflection.
The mirage effect illustrates light's bending and varying speed in different temperatures.

Plane Mirror

A flat, polished surface reflects light, producing virtual and erect images located equidistantly from the mirror.
Images can be classified as real or virtual, erect or inverted, magnified or diminished.

Principle of Reversibility of Light

Light rays retrace their paths when their direction is reversed after reflection.

Spherical Mirrors

Spherical mirrors are made from concave or convex shapes, reflecting light differently.
The focal length (F) is half the radius of curvature (R); F = R/2.

Characteristics of Spherical Mirrors

Key terms include pole (P), center of curvature (C), radius of curvature (r), and principal axis.
Ray diagrams aid in understanding image formation under various conditions.

Mirror Formula

The mirror formula relates object distance (u), image distance (v), and focal length (f): 1/v + 1/u = 1/f.

Refraction and Refractive Index

Refraction occurs when light passes from one medium to another, bending based on the media's refractive indices.
The relative refractive index is calculated as n = c/v, where c is the speed of light in vacuum, and v is the speed in the medium.

Total Internal Reflection

Occurs when light travels from denser to rarer mediums; critical angle must be exceeded for reflection instead of refraction.
Example applications include optical fibers and mirages.

Spherical Lenses

Made by binding two spherical surfaces; convex lenses converge light, while concave lenses diverge it.
Important terms include optical center (P), principal axis, focus (F), and focal length.

Lens Formula and Power

Lens formula is 1/v = 1/u = 1/f, illustrating the relationships between object distance, image distance, and focal length.
Power of a lens is defined as 1/f (in meters), measured in diopters (D).

Applications of Lenses

Spherical lenses are utilized in spectacles, binoculars, magnifying glasses, and telescopes.

Sample Problems

The refractive index of diamond with respect to carbon disulfide calculated as 1.48.
Focal length of a mirror with an object 20 cm from it, yielding an image 15 cm behind, calculated as 60 cm.
Image height from a concave lens with a 3 cm high object placed 80 cm away, resulting in a 0.6 cm tall image.

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Description

This quiz covers the fundamental concepts of light, including its properties, behavior, and laws of reflection. Explore wave-particle duality and the applications of Fermat's principle in the propagation of light. Test your understanding of how light interacts with different surfaces and media.