Notes on Refraction of The Light | Grade 8 > Science > Light | KULLABS.COM

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An object that lets light pass through it is called a medium. Light does not need a medium to travel, unlike sound because it is capable of travelling through space. The bending of light as, it passes from one transparent medium to another medium, is called refraction of light. It occurs because light travels at the lower speed in an optically denser medium. It is due to refraction that a pencil appears bent when dipped obliquely in water.

#### Laws of refraction: 1. The incident ray, the normal and the refracted ray all lie in the same plane.
2. The ray of light bends towards the normal when it passes from a rarer medium to a denser medium and away from the normal when it passes from the denser medium to the rarer medium.
3. If a ray of light travels normally ( i = 0), it goes straight.

The position and nature of the image formed by concave lens

 S.no. Position of object Position and nature of image formed 1. At infinity, Image is real, inverted, small size and forms at A. 2. Beyond C, Image is real, inverted and smaller size. Image is formed between F and C. 3. At C, Image is real, inverted and small in size. Image is formed at C. 4. Between F and C Image is real, inverted and magnified. Image is formed beyond C. 5. At F, Image is real, inverted and highly magnified. Image is formed at infinity. 6. Between pole, O and F Image is virtual, erect and magnified. Image is formed behind the mirror.  Activity

1. Place a clean sheet of white sheet on the table
2. Place a glass slab on the table.
3. Draw the outline of glass slab with the help of pencil in the paper. Name the outline ABCD.
4. As in the figure, place a pin at P and Q at the side of AB. P and Q should be 8 cm far.
5. Looking from the other side of the glass slab fix two pins R and S such that your eye and the feet of all the pins lie in one straight line.
6. Now remove glass slab and pins
7. Now join two point P and Q and stretch up to the X.
8. Join two point R and S and stretch up to the Y.
9. Join point X and Y.
10. Strech PQ up toZ.
11. Draw line MN from point X and M1M2from point Y.

Here, the ray from the air, PX is incident ray. Ray passing from glass slab XY is refracted ray. YS ray is emergent ray. XY is an actualpath of ray PQ, Here PX ray bends towards the normal. XY ray again bends away from M1M2. This experiment shows that ray bends when it travels from one medium to another.

• The bending of light as it passes from one transparent medium to another medium is called refraction of light.
• Laws of refraction:
1. The incident ray, the normal and the refracted ray all lie in the same plane
2. The ray of light bends towards the normal when it passes from a rarer medium to a denser medium and away from the normal when it passes from denser medium to rarer medium.
3. If a ray of light travels normally (< i = 0), it goes straight.
.

### Very Short Questions

The laws of refraction are:

• The incident ray, the normal and the refracted ray all lie in the same plane.
• The ray of light bends towards the normal when it passes from a rarer medium to a denser medium and away from the normal when it passes from the denser medium to the rarer medium.
• If a ray of light travels normally ( i = 0), it goes straight.

Due to refraction of light, the light rays coming from the apparent position of the fish appears shorter eyes and he hits the spear at that point but the fish does not get hit because the actual position of the fish is slightly below that of apparent position of the fish.

The process of bending of light as it passes from one medium to another medium is called refraction of light.  AO → incident ray
OB → refracted ray
BC → emergent ray
MN and M'N' = normal
∠AOM = Angle of incidence
∠BON = Angle of refraction

The velocity of light in rarer medium is greater than velocity of the light in denser medium. So, because of the variation of speed of light in two medias, the light bends which is the main cause of refraction.

1. A stick partly immersed in water and placed inclined to the surface, appears bent at the surface.
2. A swimming pool appears shallower than it really is.

The laws of refraction are as follows:

1. The incident ray, refracted ray and the normal lies in the same point of a plane.
2. A ray of light bends towards the normal when it travels from rarer medium to denser medium and bends away from the normal when it travels from denser medium to rarer medium.
3. The ratio of sine of angle of incidence (Sin i) to the sine of angle of refraction (sin r) is always constant for a given pair of media.
Mathematically, = µ (constant)
The constant quantity 'µ' is called refractive index.

The refractive index of a medium is defined as the ratio of velocity light in air (or vacuum) to the velocity of the light in the medium.
∴ RI of a medium = 1. The refraction of light is shown in the figure.
2. In the given figure:
AO → incident ray
OB → refracted ray
BC → emergent ray
MN = normal
∠AOM = Angle of incidence
∠BON = Angle of refraction
3. Since the refracted ray bends towards the normal, we can say light comes from the rarer medium (water) and falls to denser medium (glass). When a beam of light travels from denser medium to rarer medium, it bends away from the normal. So, the angle of refraction is greater than the angle of incidence.

1. The refraction of light is shown in the figure.
2. Due to refraction of light, the light ray coming from the parts of pipe inside the water gets bent at the surface of the water. These deviated rays appear on our eyes and the parts of ruler inside the water appear bent.

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• ### The phenomenon of bending of light when changing medium is called ______.

diffraction of light

reflection of light

refraction of light

interference of light

• ### When passing from rarer to denser medium the light ______.

bends away from the normal

depends on energy of the light beam

does not bend at all

bends towards the normal

• ### When passing from denser to rarer medium the light ______.

does not bend at all

bends towards the normal

bends away from the normal

depends on energy of the light beam

• ### When passing from denser to rarer medium at an angle of 900 light ______.

depends on energy of the light beam

does not bend at all

bends away from the normal

bends towards the normal

oil

glass

vacuum

water

• ### When the object is at infinity then image is ______.

real, inverted and small in size

virtual, erect and small size

virtual, inverted and small size

real, erect and small size

• ### Which image is formed when the object is placed  between F and C in concave mirror ?

Image is virtual, inverted and magnified. Image is formed beyond C.
Image is virtual, erect and magnified. Image is formed beyond C.
Image is real, inverted and magnified. Image is formed beyond C.
Image is real, inverted and magnified. Image is formed at C.
• ### When the object is between pole, O and F then ______.

Image is virtual, inverted and magnified. Image is formed behind the mirror.

Image is real, erect and diminished. Image is formed behind the mirror.

image is real, erect and magnified. Image is formed behind the mirror.

image is virtual, erect and magnified. Image is formed behind the mirror.

• ### When the object is at F then______.

image is virtual, inverted and highly magnified. Image is formed at infinity.

image is real, erect and highly magnified. Image is formed at infinity.

image is real, inverted and diminished. Image is formed at infinity.

image is virtual, inverted and diminished. Image is formed at infinity.

• ### When the object is at C then______.

image is virtual, inverted and small in size. Image is formed at C.

image is real, inverted and small in size. Image is formed at C.

image is virtual, erect and small in size. Image is formed at C.

image is virtual, inverted and magnified. Image is formed at C.

• ### When the object is beyond C then______.

image is real, erect and smaller size. Image is formed between F and C.

image is virtual, inverted and smaller size. Image is formed between F and C.

image is real, inverted and magnified. Image is formed between F and C.

image is real, inverted and smaller size. Image is formed between F and C.

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Concave mirror is used in touch lights as a reflector