Refraction of Light

Introduction

The refraction of light is the bending of light rays as they pass from one medium to another, thereby changing the path of the rays. Refraction occurs due to a change in the speed of the light ray or wave. The speed of light is greatest in a vacuum. When the light rays travel from a rarer to a denser medium, they bend towards the normal. If the light rays travel from a denser to a rarer medium, they bend away from the normal. The greater the density of the media, the higher the refractive index. 

This phenomenon is responsible for many interesting effects we observe in daily life, from lenses in spectacles to the colors of a rainbow.

What is Refraction of Light?

When light passes from one medium (like air) into another medium (like water or glass), its speed changes, which causes it to change direction. This bending of light is known as refraction.

Example: A pencil appears bent when placed in a glass of water.

Causes of Refraction

Refraction of light occurs when light passes from one medium to another and changes its speed, causing it to change direction. The main causes of refraction are:

1. Change in Medium:

Light bends when it moves from one transparent medium (like air) to another (like water or glass) due to a change in density.

2. Change in Speed of Light:

Light travels at different speeds in different media. When it slows down (e.g., from air to water), it bends towards the normal; when it speeds up (e.g., from water to air), it bends away from the normal.

3. Wavelength Change:

As light enters a different medium, its wavelength changes, contributing to the change in direction.

Types of Refraction

The refraction of light occurs in different ways depending on the medium through which the light travels. 

Refraction from denser to rarer medium - When light rays pass through rarer to a denser medium, the light rays bend towards the normal. Due to this the angle of refraction is smaller than the angle of incidence. e.g. In the case when light rays pass from air to water or from air to glass, it bends towards normal. It is because of the reason that the speed of light rays reduces while passing from air to glass or water.

Refraction from rarer to denser medium - When light rays pass from denser to rarer medium, the light rays bend away from the normal. Due to this the angle of refraction becomes more than the angle of incidence. e.g. In case when light rays pass from water to air or glass to air, light rays bend away from the normal. The speed of light rays becomes greater while passing from glass or water to air. 

Laws of Refraction:

1. First Law: The incident ray, the refracted ray, and the normal all lie in the same plane.

2. Second Law (Snell’s Law): The ratio of the sine of the angle of incidence to the sine of the angle of refraction is constant for a given pair of media.

Applications of Refraction in Daily Life

1. Lenses in Spectacles and Cameras

Convex and concave lenses bend light to correct vision defects or focus images in cameras.

Spectacles (Eyeglasses)

Lenses in spectacles bend (refract) light rays to help focus them properly on the retina.

People who are short-sighted (myopia) or long-sighted (hypermetropia) have eyes that do not focus light correctly.

Spectacle lenses correct this by refracting light before it enters the eye:
Concave lenses diverge light for short-sighted people.
Convex lenses converge light for long-sighted people.

Cameras:
A camera lens uses refraction to focus light rays onto the camera sensor or film.
When light passes through the camera lens, it bends and comes to a focus to form a clear image.
Just like the human eye, the camera lens changes the direction of light to get a sharp image.

2. Apparent Depth of Water

Water in a tank or pool appears shallower than it actually is due to the bending of light.

 

Light rays from the bottom of the water travel from water to air and bend away from the normal because water is denser than air.

 

Our eyes trace the light rays back in a straight line, so the bottom appears to be at a higher position than it really is.

3. Twinkling of Stars

Starlight bends as it passes through layers of Earth's atmosphere with varying densities.

Stars appear to twinkle because of refraction of light in the Earth’s atmosphere.

Light from a star travels through different layers of the Earth’s atmosphere.

Each layer has different temperatures and densities, so light bends (refracts) again and again.

This bending is not steady—the air keeps moving, so the path of light changes constantly.

As a result, the star’s light seems to shift or flicker, making it twinkle.

4. Formation of Rainbows

Rainbows are formed due to a combination of refraction, reflection, and dispersion of sunlight in raindrops.

Refraction:

When sunlight enters a raindrop, it bends because light travels slower in water than in air.

Dispersion:

Inside the raindrop, white sunlight splits into seven colours (VIBGYOR – Violet, Indigo, Blue, Green, Yellow, Orange, Red) .

Internal Reflection:

The light bounces off the inside of the raindrop.

 Refraction again:

As the light exits the raindrop, it bends again and spreads out, reaching our eyes as a beautiful rainbow.

5. Magnifying Glasses and Microscopes

These devices use convex lenses to magnify tiny objects by refracting light rays.

Magnifying Glass

It uses a convex lens (curved outward).

When light rays from an object pass through the lens, they bend (refract) and come together.

This forms a larger, upright image that appears closer to your eyes.

 Microscope:

A microscope has two or more convex lenses.

Light from the tiny object bends through these lenses, making the image larger and clearer.

Refraction helps in magnifying the image step-by-step through the lenses.

6. Prism Dispersion

When white light enters a prism, it bends (refracts) because light travels slower in glass than in air.

 

Each colour bends by a different amount:

Violet bends the most,

Red bends the least.

This causes the colours to spread out, forming a spectrum.

7. Mirages in Deserts or Roads

A mirage is an optical illusion where we see water on a hot road or in a desert, but it's not really there.

 

On hot days, the air near the ground is very hot, while the air above is cooler.

Light from the sky bends (refracts) as it passes through these layers of air with different temperatures.

This bending makes the light curve upward.

 

We think the light is coming straight from the ground, so we see a reflection of the sky, which looks like water.

 

8. Optical Fibers

Optical fibers are thin, flexible glass or plastic wires that carry light signals over long distances. They are used in the internet, medical instruments, and communication systems.

 

How Refraction Helps:

Light enters the fiber and bends (refracts) as it moves from air into the glass.

 

Inside the fiber, light travels by total internal reflection—bouncing off the walls without escaping.

 

This is possible due to the refraction and bending of light at the boundary between two materials (core and cladding).

 

9. Peepholes in Doors

A peephole lens uses refraction to let you see a wide-angle view from outside your door.

 

How Refraction Helps:

A peephole uses convex lenses arranged together.

 

When light from outside enters the peephole, the lenses bend (refract) the light rays.

 

This allows a person inside to see a wider view of the area outside, even though the hole is small.

10. Camera and Projector Lenses

Camera Lenses

A camera uses convex lenses to focus light rays from an object.

 

When light passes through the lens, it bends (refracts) and comes together to form a clear, sharp image on the camera’s sensor or film.

 

By adjusting the lens, the camera can focus on objects at different distances.

 

Projector Lenses

A projector also uses convex lenses to bend and focus light rays.

 

It projects an image from a small slide or digital source onto a large screen.

 

The lens system refracts the light so that the image is enlarged and clear on the screen.

 

11. Object Appearing Displaced in Water

A coin at the bottom of a glass of water looks shifted when viewed from an angle.

 How Refraction Helps:

 Light rays from the coin bend (refract) as they pass from water (denser) to air (rarer).

 This bending makes the coin appear closer to the surface than it really is.

Our eyes trace the light rays in a straight line, so the coin appears raised or shifted.

12. Bent Straw Effect:

A straw in a glass appears broken or bent due to refraction at the air-water surface.

How Refraction Helps:

Light rays from the part of the straw inside water travel through water (denser) and enter air (rarer).

As light moves from water to air, it bends away from the normal (refraction).

Our eyes trace these bent rays in a straight line, so the straw appears to be at a different position.

This makes the straw look bent or shifted at the water’s surface.

Conclusion

Refraction of light is a fascinating and useful phenomenon that helps us in numerous ways—from helping us see clearly to enabling modern technology like fiber optics and cameras. Understanding refraction also deepens our appreciation of nature and science.

Refraction of light is a natural and essential phenomenon that has a wide range of practical applications in both everyday life and scientific technology. It occurs when light passes from one medium to another, such as from air to water or from air to glass, causing the light to bend due to a change in its speed. This bending of light allows us to see things differently and use this effect in useful ways.

Bibliography 

https://www.geeksforgeeks.org/real-life-applications-of-refraction-of-light/

https://byjus.com/physics/refraction-of-light/

https://www.vedantu.com/question-answer/give-5-examples-of-refraction-of-light-in-daily-life

https://study.com/learn/lesson/what-is-refraction-examples.html

https://www.embibe.com/exams/effects-of-refraction-of-light