P.3.3.2.3 Refraction at a plane surface

A ray of light is incident on a glass–air boundary of a rectangular block as shown.

The refractive index of this glass is 1.5

The refractive index of air is 1.0

The angle of incidence of the light at the first glass–air boundary is 44°

What is the path of the ray of light?

• A

• B

• C

• D

Rays of light are incident at the same angle θ on the core–cladding boundary of optical fibres P and Q. The cores of P and Q have the same refractive index n.

P and Q are the same length L. The core diameter of P is half that of Q.

The time for the ray to travel along optical fibre P is (nL)/(csinθ) where c is the speed of light in a vacuum.

What is the time for the ray to travel along optical fibre Q?

• 
• 
• 
• 

An electromagnetic wave enters a fibre-optic cable from air. On entering the cable, the wave slows down to three-fifths of its original speed.

What is the refractive index of the core of the fibre-optic cable?

• 0.67

• 1.33

• 1.50

• 1.67

The diagram shows part of the path of a ray of light through a right-angled prism.

The prism is made of glass of refractive index 1.5.

The incident light ray is parallel to the face XY. The ray is refracted towards the face XY.

What is the path of the ray after it is incident on face XY?

• 
• 
• 
• 

Which row shows the change in velocity, frequency and wavelength of an electromagnetic wave as it travels from an optically less dense to an optically more dense medium?

• A

• B

• C

• D

The diagram shows a ray of light travelling in air and incident on a glass block of refractive index 1.5.

What is the angle of refraction in the glass?

• 22.5°

• 23.3°

• 33.1°

• 59.4°

A layer of liquid of refractive index 1.6 covers the horizontal flat surface of a glass block of refractive index 1.5. A ray of light strikes the boundary between them at an angle such that it travels along the boundary afterwards.

How does the ray strike the boundary?

• it travels in glass at an angle of 70° to the boundary

• it travels in glass at an angle of 20° to the boundary

• it travels in the liquid at an angle of 70° to the boundary

• it travels in the liquid at an angle of 20° to the boundary

Monochromatic light may be characterised by its speed, frequency and wavelength. Which of the following quantities change when monochromatic light passes from air into glass?

• Speed only.

• Speed and wavelength only.

• Speed and frequency only.

• Wavelength and frequency only.

Which of the following is correct when total internal reflection occurs?

• the angle of incidence is less than the critical angle

• the light meets an optically less dense medium

• the light enters a medium with a higher refractive index

• the angles that the incident and refracted rays make with the normal are the same

What is the speed of light in glass of refractive index 1.42?

• 4.26 × 10⁷ m s⁻¹

• 2.11 × 10⁸ m s⁻¹

• 3.00 × 10⁸ m s⁻¹

• 4.73 × 10⁸ m s⁻¹