Light enters an optical fiber at an angle of incidence of 15 ∘ . On a copy of this drawing, draw a line to show how the path of the light continues down the fiber.

The ray of light entering in the fiber is totally internally reflected every time as it strikes the interface of the two media. It follows the laws of reflection every time as it gets reflected. The reflected ray and the incident ray forms the equal angle with the normal drawn at the point of incidence. The path of light is shown in the figure below:

Light enters an optical fiber at an angle of 15 ∘ . The refractive index of the fiber is 1 . 4 . Calculate the critical angle for this optical fiber.

When light travels from a denser medium to another medium and the angle of incidence is equal to the critical angle then the refracted light ray grazes the interface of two media. The critical angle i c and refractive index of the denser medium with respect to the rarer medium is given by the formula: μ = 1 sin i c ⇒ sin i c = 1 μ = 1 1 . 4 = 0 . 715 ⇒ i c = sin - 1 0 . 715 = 45 . 6 ∘

Light enters an optical fiber at an angle of 15 ∘ . The refractive index of the fiber is 1 . 4 . Calculate the speed of light in the fibre.

The speed of light is maximum in air or vacuum. Consider that the light is travelling from medium 1 into medium 2 . Then the Refractive index of the material of the medium 2 is defined as the ratio of the speed of light in the two media and is given by the formula: n 21 = v 1 v 2 ........(i) Given: The refractive index of fibre n 21 = 1 . 4 .....(ii) The speed of light in air v 1 = 3 × 10 8 m s - 1 .....(iii) Using (i), (ii) and (iii), the speed of light in the fibre: v 2 = v 1 n 21 = 3 × 10 8 1 . 4 = 2 . 14 × 10 8 m s - 1

E M B I B E

MYP Physics A concept-based approach Years 4&5>Chapter 9 - Development>Exercise 7>Q 2

EASY

MYP:4-5

IMPORTANT

Earn 100

What would be the refractive index of a material have to be in order to have a critical angle of $30 °$ ?

Important Questions on Development

EASY

MYP:4-5

IMPORTANT

MYP Physics A concept-based approach Years 4&5>Chapter 9 - Development>Exercise 7>Q 3

Why doesn't total internal reflection occur when light travels from air into water?

MEDIUM

MYP:4-5

IMPORTANT

MYP Physics A concept-based approach Years 4&5>Chapter 9 - Development>Exercise 7>Q 4

Sound waves speed up when they enter water. In air, the speed is about

330 m s^{- 1}

, but in water the sound waves travel at about

1500 m s^{- 1}

. Explain whether total internal reflection will occur when sound travels from air into water and from water into air. Explain how this affects how well you can hear sounds above the surface of the water if you are under the surface.

EASY

MYP:4-5

IMPORTANT

MYP Physics A concept-based approach Years 4&5>Chapter 9 - Development>Exercise 8>Q 1

A tennis player can serve a tennis ball at