Page 1 - 10-phy-12 Geometrical Optics
P. 1
12Geometrical Optics
Experiment Verify the laws of refraction of light using
a glass slab.
12.1
Date ________________
It has been observed that when light travels from one medium to another,
Background its speed changes. In a denser medium the speed of light is less than the speed in a
Information rarer medium. When the light rays are incident obliquely to the denser medium,
they bend towards the normal at the point of incidence and in case of rarer
medium they bend away from the normal. This bending of light is called
refraction. It is to be noted that incident light rays along normal go straight
through the mediums without bending. There are two laws of refraction stated as:
1. Incident ray, refracted ray and the normal at the point of
incidence, all lie in the same plane.
2. The ratio of the sine of angle of incidence and the sine of angle of
refraction is constant. This is called Snell's law. This ratio is also
known as refractive index n of denser medium with respect to a
rarer medium.
DO YOU KNOW? n = sin i
sin r
Apparent position
Sun
Observer M
Sun Earth P Incident ray N
Actual position
The rays from the Qi B
Sun coming through A
space enter the Earth's
atmosphere that is a X
denser medium. They
bend slightly towards the r
normal and appear above
the horizon. Thus the Sun N¢ Refracted ray
appears to rise a few
minutes earlier than the S
actual rise. Similar effect i¢
happens at sunset. The
sun sets few minutes later. D Y r¢ Emergent C
Hence, a day become S¢
about 4 minutes longer. R
ray
S
Fig. 12.1.1
3
Experiment Verify the laws of refraction of light using
a glass slab.
12.1
Date ________________
It has been observed that when light travels from one medium to another,
Background its speed changes. In a denser medium the speed of light is less than the speed in a
Information rarer medium. When the light rays are incident obliquely to the denser medium,
they bend towards the normal at the point of incidence and in case of rarer
medium they bend away from the normal. This bending of light is called
refraction. It is to be noted that incident light rays along normal go straight
through the mediums without bending. There are two laws of refraction stated as:
1. Incident ray, refracted ray and the normal at the point of
incidence, all lie in the same plane.
2. The ratio of the sine of angle of incidence and the sine of angle of
refraction is constant. This is called Snell's law. This ratio is also
known as refractive index n of denser medium with respect to a
rarer medium.
DO YOU KNOW? n = sin i
sin r
Apparent position
Sun
Observer M
Sun Earth P Incident ray N
Actual position
The rays from the Qi B
Sun coming through A
space enter the Earth's
atmosphere that is a X
denser medium. They
bend slightly towards the r
normal and appear above
the horizon. Thus the Sun N¢ Refracted ray
appears to rise a few
minutes earlier than the S
actual rise. Similar effect i¢
happens at sunset. The
sun sets few minutes later. D Y r¢ Emergent C
Hence, a day become S¢
about 4 minutes longer. R
ray
S
Fig. 12.1.1
3
