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.

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.

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 water. These deviated rays appear on our eyes and the parts of ruler inside the water appear bent.

1. The incident ray must pass from denser medium to rarer medium.
2. The angle of incidence must be greater than the critical angle.

1. glass = 420
2. water = 490
3. diamond = 240

It means that the ray is passing from glass to air such that the angle of incidence is 42⁰ while the angle of refraction is 90⁰.

1. It is called critical angle and its value is 42⁰.
2. When the ∠IOM is further increased, then there occurs total internal reflection and all the rays reflect in the glass medium.

1. To view the internal parts of the body as in endoscopy
2. For receiving and transmitting electric signals in cables

1. Mirage
2. Sparkling of diamond

In summer, in the coal tarred roads or in the deserts, optical illusion is observed due to total internal reflection of light. This phenomenon is called mirage.

1. Light pipe or optical fibers work on the principle of total internal reflection.
2. It is used to construct instruments like binoculars.

Solution:
Here,
Speed of light in air (c) = 3 x 10⁸ m/s
Speed of light in glass (v) = 2 x 10⁸ m/s
RI of glass (µ) = ?
Now,
µ = = = 1.5

Solution:
Here,
Speed of light in air (c) = 3 x10 \(^{8}\) m/s
Speed of light in diamond (v) =?
RI of diamond(µ) = 2.42
Now,
µ =
or, v =
or, v =
or, v = 1.24 x 108 m/s
Hence, the speed of light in diamond is 1.24 x10 \(^{8}\) m/s.

Here,
Angle of incidence (i) = 20\(^{0}\)
Refractive index of glass (µ) = 1.5
Angle of refraction (r) = ?

We know that ,
µ = \(\frac{sin\;i}{sin\;r}\)
1.5 = \(\frac{sin\;20}{sin\;r}\)
sin r = \(\frac{sin\;20}{1.5}\)
or, r = sin \(^{-1}\) \(\frac{0.3420}{1.5}\) = 13.18 \(^{o}\)

Therefore, the angle of refraction in glass is13.18 \(^{o}\)

Here, Real depth = 2m
R.I. of water = 1.33
Apparent depth = ?
We have,
R.I. = \(\frac{Real\;Depth}{Apparent\;depth}\)
or, 1.33 = \(\frac{2}{Apparent\;Depth}\) = 1.503 m
\(\therefore\) Apparent Depth of the pond is 1.503 m.

Here ,
Refractive index of diamond (µ) = 2.42
Critical angle (C) = ?

We know ,
\(\therefore\)
SinC = \(\frac{}1{µ}\)
or, C = \(sin^{-1}\) ( \(\frac{1}{2.42}\) ) = 24.41 \(^0\)C

Therefore, the critical angle of diamond is 24.41 \(^0\)C .

Here,
Resistance (R) = 2Ω
Current (I) = 2A
Potential Difference = ?

From, Ohm's law, we have
V = IR
V = 2 \(\times\) 2
\(\therefore\) V = 4V

Hence , the potential difference is 4V.

Diameter (d) = 0.44 \(\times\) \(10^{-4}\)m
Resistance (R) = 10Ω
Resistivity (ρ) = 4.43 \(\times\) \(10^{-7}\) Ωm
Length (l) = ?
We know,
R = ρ \(\frac{1}{A}\)
or, R = ρ \(\frac{1}{πd^2}\) \(\times\)4
10 = \(\frac{4.43 \times 10^{-7} \times l \times 4}{\frac {22}{7} 4.4 \times 10^{-4} \times 4.4 \times 10^{-4} }\)
l = \(\frac{10 \times 22 \times 4.4 \times 4.4 \times 10^{-8} }{7 \times 4.43 \times 4 \times 10^ {-7} } \)
or, l = \(\frac{4.26 \times 10^{-5}}{1.24 \times 10^{-5} }\)
= 3.42

Hence, the length of the manganin wire is 3.42 m.