New Senior Secondary Physics Compulsory: Wave Chapter 2 Refraction of Light

Page 1

CHAPTER 2 REFRACTION OF LIGHT

1 Nature of Refraction

Travelling Speed and Refraction

2 Speed of light and refractive index

Speed of light in different media

Medium Speed of Light within medium Refractive Index

Vacuum 8 -12.998 10 ms×

Air 8 -12.997 10 ms×

Water 8 -12.254 10 ms×

Glass 8 -11.999 10 ms×

Diamond 8 -11.239 10 ms×

Refractive Index

New Senior Secondary Physics Compulsory: Wave Chapter 2 Refraction of Light

Page 2

3 Refraction of Light Basic Configuration

Bending Direction

Law of Refraction

New Senior Secondary Physics Compulsory: Wave Chapter 2 Refraction of Light

Page 3

Explanation of Snell’s Law

Calculation Examples Find the unknowns in the following situations: (a) (b)

New Senior Secondary Physics Compulsory: Wave Chapter 2 Refraction of Light

Page 4

[HKCEE] [Snell’s Law] The diagram shows a light ray travelling from liquid to air. Find the refractive index of the liquid.

[HKCEE] [Bending Direction]

A ray of light travels in air and strikes a glass block as shown above. Which of the following diagrams best shows the path of the ray?

4 Apparent Depth

Why objects under water look shallower than it actually is?

New Senior Secondary Physics Compulsory: Wave Chapter 2 Refraction of Light

Page 5

5 Total Internal Reflection

Calculate the angle of reflection for the following cases and draw the reflected ray. (a) 30oi = (b) 40oi = (c) 50oi =

Critical Angle between two media

New Senior Secondary Physics Compulsory: Wave Chapter 2 Refraction of Light

Page 6

Total Internal Reflection

Write down the two conditions for total internal reflection to happen:

Calculation Examples

Calculate the critical angles in the following configurations: (a) (b)

New Senior Secondary Physics Compulsory: Wave Chapter 2 Refraction of Light

Page 7

6 Applications of Total Internal Reflection

Optical Fibre Draw a suitable diagram to explain how light signal can be transmitted by an optical fibre.

Sparkling of Diamond By drawing a suitable diagram, explain how the high value of refractive index give the diamond sparkling appearance.

Mirage By drawing a suitable diagram, explain the formation of mirage in very hot desert.

必背位！

必背位！

必背位！

New Senior Secondary Physics Compulsory: Wave Chapter 2 Refraction of Light

Page 8

Prismatic Periscope What is the advantage of using glass prism instead of plane mirrors for reflection of light? (1 mark)

[HKCEE] [Periscope]

A student uses two triangular prisms to construct a periscope as shown above. Which of the following shows the image of the object as seen by the observer? A. ↓ B.↑ C. ↘ D.↗ E. ↖↗

FINAL REMARKS

Refraction is an important phenomenon of light since its forms the basis of lens, which serves as the most important application of optics in daily life. Historically, Snell’s law is just an experimental result dated as old as ancient Egypt. In the modern view of treating light as a wave, we can theoretically explain Snell’s law.

Students are required to be familiar with refraction calculation, and the calculation of total internal reflection. Students should be able to explain some daily life phenomenon due to refraction and total internal reflection, such as apparent depth, sparkling of diamond and the formation of mirage.

必背位！