Refraction is the bending of light (it also happens with Sound, water and other waves) as it passes from one transparent substance into another. This bending by refraction makes it possible for us to have lenses, magnifying glasses, prisms and rainbows. Even our eyes depend upon this bending of light. Without refraction, we wouldn’t be able to focus light onto our retina.
Law of refraction
The law of refraction, which is generally known as Snell’s law, governs the behaviour of light-rays as they propagate across a sharp interface between two transparent dielectric media. Consider a light-ray incident on a plane interface between two transparent dielectric media, labelled 1 and 2, as shown in Fig. 57. The law of refraction states that the incident ray, the refracted ray, and the normal to the interface, all lie in the same plane. Furthermore,
where $theta_1$ is the angle subtended between the incident ray and the normal to the interface, and $theta_2$ is the angle subtended between the refracted ray and the normal to the interface. The quantities $n_1$ and $n_2$ are termed the refractive indices of media 1 and 2, respectively. Thus, the law of refraction predicts that a light-ray always deviates more towards the normal in the optically denser medium: i.e., the medium with the higher refractive index. Note that $n_2>n_1$ in the figure. The law of refraction also holds for non-planar interfaces, provided that the normal to the interface at any given point is understood to be the normal to the local tangent plane of the interface at that point.
Refraction by glass slab
To understand the refraction of light through a glass slab consider the figure given below which shows the refraction of light through a rectangular glass slab.
Here in this figure AO is the light ray travelling in air and incident on glass slab at point O.
Now on entering the glass medium this ray bends towards the normal NN’ that is light ray AO gets refracted on entering the glass medium.
After getting refracted this ray now travels through the glass slab and at point B it comes out of the glass slab as shown in the figure.
Since ray OB goes from glass medium to air it again gets refracted and bends away from normal N1N’1 and goes in direction BC.
Here AO is the incident ray and BC is the emergent ray and they both are parallel to each other and OB is the refracted ray.
Emergent ray is parallel to incident ray because the extent of bending of the ray of light at the opposite parallel faces which are PQ (air-glass interface) and SR (glass-air interface) of the rectangular glass slab is equal and opposite.
In the figure i is the angle of incidence, r is the angle of refraction and e is the angle of emergence.
Angle of incidence and angle of emergence are equal as emergent ray and incident ray are parallel to each other.
When a light ray is incident normally to the interface of two media then there is no bending of light ray and it goes straight through the medium.
critical angle
The critical angle is defined as the angle of incidence that provides an angle of refraction of 90-degrees. Make particular note that the critical angle is an angle of incidence value. For the water-air boundary, the critical angle is 48.6-degrees. For the crown glass-water boundary, the critical angle is 61.0-degrees. The actual value of the critical angle is dependent upon the combination of materials present on each side of the boundary.
,
Refraction is the bending of light as it passes from one medium to another. This happens because light travels at different speeds in different media. The speed of light in a vacuum is the fastest, and the speed of light in a denser medium is slower. When light passes from a less dense medium to a denser medium, it bends towards the normal, which is an imaginary line perpendicular to the interface between the two media. When light passes from a denser medium to a less dense medium, it bends away from the normal.
The laws of refraction are two laws that describe how light bends when it passes from one medium to another. The first law of refraction states that the incident ray, the refracted ray, and the normal all lie in the same plane. The second law of refraction states that the ratio of the sine of the angle of incidence to the sine of the angle of refraction is a constant for a given pair of media. This constant is called the index of refraction.
The index of refraction is a measure of how much light bends when it passes from one medium to another. It is a dimensionless number that is greater than or equal to 1. The index of refraction of air is 1.0003, the index of refraction of water is 1.33, and the index of refraction of glass is 1.52.
Total Internal Reflection is a phenomenon that occurs when light passes from a denser medium to a less dense medium at an angle greater than the critical angle. The critical angle is the angle of incidence at which the refracted ray grazes the boundary between the two media. When light passes through the critical angle, it is completely reflected back into the denser medium.
Refraction in curved surfaces can be used to create lenses and prisms. Lenses are curved pieces of glass that are used to focus or diverge light. Prisms are triangular pieces of glass that are used to split white light into its component colors.
Rainbows are an optical and meteorological phenomenon that causes a spectrum of light to appear in the sky when the Sun shines onto droplets of moisture in the Earth’s Atmosphere. Rainbows can be full circles. However, the observer normally sees only an arc formed by illuminated droplets above the ground, and centered on a line from the Sun to the observer’s eye.
Refraction is a fascinating phenomenon that has many practical applications. It is used in lenses, prisms, and other optical devices. It is also responsible for many natural phenomena, such as rainbows.
What is light?
Light is a form of energy that travels in waves. It can travel through space, air, water, and other transparent materials. Light can also be reflected off of surfaces.
What is refraction?
Refraction is the bending of light as it passes from one medium to another. This happens because light travels at different speeds in different materials. When light passes from a material with a high speed to a material with a low speed, it bends towards the normal. When light passes from a material with a low speed to a material with a high speed, it bends away from the normal.
What are the laws of refraction?
The first law of refraction states that the incident ray, the refracted ray, and the normal all lie in the same plane. The second law of refraction states that the ratio of the sine of the angle of incidence to the sine of the angle of refraction is a constant for a given pair of media. This constant is called the refractive index.
What are some examples of refraction?
Some examples of refraction include:
When you look at a straw in a glass of water, the straw appears to be bent. This is because the light from the straw is refracted as it passes from the air into the water.
When you see a rainbow, the light from the sun is refracted as it passes through the water droplets in the air.
When you look at a star in the night sky, the light from the star is refracted as it passes through the Earth’s atmosphere. This is why stars appear to twinkle.
What are some applications of refraction?
Some applications of refraction include:
Lenses: Lenses are used in many optical devices, such as eyeglasses, cameras, and microscopes. Lenses work by refracting light to focus an image on a surface.
Prisms: Prisms are used to split white light into its component colors. This is why you see a rainbow when you look through a prism.
Fiber optics: Fiber optic cables are used to transmit light over long distances. The light is refracted as it passes through the cable, which allows it to travel without being scattered.
What are some misconceptions about refraction?
Some common misconceptions about refraction include:
The speed of light is the same in all materials. This is not true. The speed of light is different in different materials.
Refraction only happens when light passes from one medium to another. This is not true. Refraction can also happen when light passes through a medium that is not uniform.
Refraction is the same as reflection. This is not true. Refraction is the bending of light, while reflection is the bouncing of light.
What is the future of refraction research?
Refraction is a well-studied phenomenon, but there are still some areas where research is needed. One area of interest is the development of new materials with unusual refractive properties. Another area of interest is the study of how refraction affects the behavior of light in complex systems, such as optical fibers.
Sure. Here are some MCQs without mentioning the topic Refraction of Light:
When light travels from one medium to another, it bends. This is called refraction. What causes refraction?
(A) The change in speed of light
(B) The change in wavelength of light
(C) The change in frequency of light
(D) The change in direction of light
The amount of refraction depends on the following factors:
(A) The angle of incidence
(B) The index of refraction of the two media
(C) The wavelength of light
(D) All of the above
The index of refraction of a medium is a measure of how much light bends when it travels from one medium to another. The higher the index of refraction, the more the light bends.
(A) True
(B) False
When light travels from air to water, it bends towards the normal.
(A) True
(B) False
When light travels from water to air, it bends away from the normal.
(A) True
(B) False
A mirage is an optical illusion that can be seen in hot, dry places. It is caused by refraction of light.
(A) True
(B) False
A rainbow is an optical and meteorological phenomenon that causes a spectrum of light to appear in the sky when the Sun shines onto droplets of moisture in the Earth’s atmosphere.
(A) True
(B) False
A lens is a piece of transparent material that is used to bend light. Lenses can be used to focus light, to spread light out, or to change the direction of light.
(A) True
(B) False
A convex lens is a lens that is thicker in the middle than it is at the edges. Convex lenses are used to focus light.
(A) True
(B) False
A concave lens is a lens that is thinner in the middle than it is at the edges. Concave lenses are used to spread light out.
(A) True
(B) False
