Define Refraction.
The changing in the direction of light, when it it passes from one medium to another obliquely, is called refraction. The medium may be be air, water, glass, or any other optical medium.
What is an optical medium?
An optical medium is a medium through which light propagates.
Define incident ray
A ray of light, striking a surface separating two different optical media, is called an incident ray.
Define angle of incidence.
The angle between the incident ray and the normal at the point of incidence, is called angle of incidence.
Define refracted ray
When an incident ray of light enters from one optical medium to another medium of different optical density, it undergoes a change in velocity and direction. This bent ray of light is now called the refracted ray.
Define angle of refraction.
The angle between the refracted ray and the normal at the point of incidence, is called angle of refraction.
Define Lateral Displacement.
When light passes obliquely through an optically denser or rarer medium and then emerges back in the same initial optical medium ( through a rectangular glass slab, for example), the perpendicular (shortest) distance between the incident ray and the emergent ray is called lateral displacement.
Define emergent ray
Emergent ray is the ray of light that comes back out in the initial optical medium, after passing through another medium of different optical density, after refraction.
Define angle of emergence
Angle of emergence is the angle made by the emergent ray with the normal at the point of emergence
Is Angle of incidence = Angle of refraction?
No. Since during refraction, there is bending of light, so, angle of incidence is not equal to the angle of refraction.
What causes refraction?
The refraction of light is due to change in the speed of light on going from one medium to another.
Refraction varies with the speed of light in the medium. Comment.
The greater the difference in the speed of light in the two media, greater is the amount of refraction (bending) of light.
What are the types of refraction?
There are two types of refraction:
- Refraction when light goes from optically rarer to denser medium- Here the refracted ray bends towards the normal- Here the refractive index is greater than 1
- Refraction when light goes from optically denser to rarer medium- Here the refracted ray bends away from the normal- Here the refractive index is less than 1
What happens when a ray of light goes from a denser medium to a rarer medium?
When a ray of light goes from a denser medium to a rarer medium, it bends away from the normal (at the point of incidence).
What happens when a ray of light goes from a rarer medium to a denser medium?
When a ray of light goes from a rarer medium to a denser medium, it bends towards the normal (at the point of incidence).
- An obliquely held pencil, partly immersed in water, appears to be bent at water surface.
- An object placed under water, appears to be raised.
- A pool of water appears less deep than it actually is.
- Upon placing a thick glass slab over a printed matter, the letters appears to be raised, when viewed from top.
- The stars appear to twinkle on a clear night sky.
- Angle of incidence
- Thickness of rectangular glass slab
- relative optical density of the two media
- refractive index of the medium
- wavelength of the ray of light
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