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Refraction of  Light Through a Rectangular Glass Block

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Topics

  • Definition: Lateral Displacement
  • Key Points: Refraction of Light Through a Rectangular Glass Block

Notes

REFRACTION: 

The change of direction of light because of change of medium is known as Refraction or Refraction of Light. The ray of light changes its direction or phenomenon of refraction takes place because of difference in speed in different media.

The light travels at faster speed in rare medium and at slower speed in denser medium. The nature of media is taken as relative. For example air is a rarer medium than water or glass.

When ray of light enters from a rarer medium into a denser medium, it bends towards normal at the point of incidence. On the contrary, when ray of light enters into a rarer medium from a denser medium it bends away from the normal.

Ray emerging after the denser medium goes in the same direction and parallel to the incident ray.

The angle between incident ray and normal is called Angle of Incidence and it is denoted as ‘i’. The angle between refracted ray and normal is called the Angle of Refraction. Angle of refraction is denoted by ‘r’.

Laws Of Refraction Of Light.

(i) The incident ray, the refracted ray and the normal to the interface of two transparent media at the point of incidence, all lie in the same plane.

(ii) The ratio of sine of angle of incidence to the sine of angle of refraction is a constant, for the light of a given colour and for the given pair of media. This law is also known as Snell’s law of refraction. (This is true for angle 0 < i < 90o) If i is the angle of incidence and r is the angle of refraction, then,

`"sinI"/"sinr"` = constant

This constant value is called the refractive index of the second medium with respect to the first.

CISCE: Class 10

Definition: Lateral Displacement

The perpendicular distance XY between the path of the emergent ray BC and the direction of the incident ray OD is called the lateral displacement.

CISCE: Class 10

Key Points: Refraction of Light Through a Rectangular Glass Block

  • In a rectangular glass block, the emergent ray is parallel to the incident ray, but laterally displaced.
  • The angle of emergence (e) is equal to the angle of incidence (i).
  • The perpendicular distance XY between the emergent ray and the incident ray's direction is called the lateral displacement.
  • Lateral displacement increases with the thickness of the block, the angle of incidence, and the refractive index, and is greater for violet light than red light.
 

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Related QuestionsVIEW ALL [218]

Calculate the velocity of light in a glass block of refractive index 1.5. (Velocity of light in air = 3 × 108 m/s)

How does the deviation produced by a prism depend on the wavelength of incident light?

A ray of light of wavelength 6600 Å suffer refraction from air to glass. Taking \[\ce{_a\mu_g = \frac{3}{2}}\], find the wavelength of light in glass.

A Water pond appears to be 2.7 m deep. If the refractive index of water is 4/3, find the actual depth of the pond. 

Write a relationship between the angle of incidence and angle of refractions for a given pair of media

In the diagram alongside a ray of light, PQ is incident normally on one face AB of an equilateral glass prism. What is the angle of incidence at the faces AB and AC?

Explain how the formation of a rainbow occurs.

After a robbery, if a window has been broken, there will be tiny particles of glass. Some of these will be found at the scene of the crime and some may be caught in the thief’s clothing. If the police can prove that these particles are identical, they have a strong case.
A method of doing this is to suspend the particles of glass in a special liquid. Light of a single colour is thrown through the liquid and the particles viewed through a microscope. The temperature of the liquid is then slowly altered. This alters the speed of light through the liquid (i.e., it alters the refractive index). At one particular temperature, the particles of glass disappear. It this happens at the same temperature for both sets of glass particles, they probably came from the same broken pane of glass.
Complete and copy the diagram to show how light bends when it travels from the liquid to the glass and back to the liquid, If the light slows down in the glass.

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