## Course Description

### Overview

This course is targeted at Singapore Cambridge GCE O level students, but is also relevant to IGCSE students and Singapore's Integrated program students.

Tired of fumbling around in the dark with vague explanations and difficult formulas? This course covers all the fundamental concepts of light in short, easy-to-understand videos with a focus on understanding physics phenomena and the reasons why each of these formulas appear the way they are. We guarantee that this will be an illuminating experience.

### Course Content

You will learn:

• How light reflects
• How light refracts
• Snell's law, refractive index and total internal reflection
• The weird and wacky effects of thin converging lenses
• The equally weird and wacky effects of thin diverging lenses
• Why you only need a mirror half as tall as you are to see your entire reflection
• Lots of other cool stuff! (Some of the videos in this course are marked as "explanation videos", which go into greater depth on the topics covered. We try to bring in out-of-syllabus concepts where possible to make things more interesting and give a more complete understanding of the topic)

A link to the full O level Physics syllabus can be found here

### Course Prerequisites

You will need to know:

• How to watch videos on your computer Math Arena

The instructor is from Math Arena.The instructor is absolutely passionate about teaching and you'll find the lessons engaging and ultimately rewarding.

## Course curriculum

• 1

### Introduction

• Subject Content Requirements

• 2

### Reflection - Basics

• Q1 Which of the following demonstrates the law of reflection?

• Q2 A plane mirror is inclined at 40 degrees to the floor. An incident ray parallel to the floor strikes the mirror and a reflected ray is formed. What is the angle of reflection?

• Q3 An incident ray strikes a plane mirror at an angle of incidence of 40 degrees. What is the decrease in the angle of reflection if the incident ray moves to an angle of incidence of 30 degrees?

• Q4 Which of the following are the properties of a plane mirror image?

• Q4 explanation

• Q5 Which of the following are the properties of a plane mirror image?

• Q6 Which of the following is the mirror image of the word “EXAMPLE” when it is placed facing the plane mirror?

• Q7 A man looked into a plane mirror and saw the clock as shown below. What was the time then?

• 3

### Reflection - Distance and speed

• Q8 An object O is placed in front of a mirror. Which is a possible position of the image?

• Q8 explanation

• Q9 Two men are standing in front of a plane mirror as shown. When a man looks into the mirror, how far away from him will man B seem to be?

• Q10 Two men are standing in front of a plane mirror as shown. If man A walks 5 m backward and then looks into the mirror, how far away from him will man B seem to be?

• Q11 A mirror periscope is used to observe a bird as shown below. How far away will the bird seem to be from the observer?

• Q12 Man A is standing in front of a plane mirror while man B is running towards him from behind. If man B is running at a speed of 1 m/s, how many meters nearer does man B seem to be away from man A after 5 seconds?

• Q13 A man is running towards a plane mirror at a speed of 2 m/s. How fast does he see himself running towards his image?

• Q14 A man is standing still while a plane mirror is moving away from him at a speed of 4 m/s, how fast does he see his image moving away?

• 4

### Reflection - Ray diagrams

• Q15 A man drills a tiny hole at the 40 cm mark of a meter long ruler. He places a 30 cm long plane mirror in front of the ruler as shown. What are the minimum and maximum readings...

• Q16 A painter leans back against a pointed wall while looking into a 1 m long mirror at the opposite end of a rectangular room. How much of the painted wall can he see through the 1 m long mirror?

• Q17 A plane mirror AB is positioned at the corner of a road as shown in the plan view below. Which men can the observer see through mirror?

• Q18 Two mirrors (facing each other) and an object O are places in the grid as shown. At which position(s) can the virtual image of object O be formed?

• Q18 explanation

• Q19 Four light bulbs are concealed from an observer by an opaque wall as shown. Without shifting the positions of the observer and the bulbs, how many bulbs can the observer see from the mirror?

• Q20 Three objects P, Q and R are viewed through a plane mirror as shown. When an obstacle is moved towards the mirror, which of the objects will disappear first and which will disappear last?

• Q21 The figure below shows Joe and Peter standing in front of an 8.0 m long mirror. Joe stands 2.0 m away from the left edge of the mirror, facing it...

• Q22 The ray from a laser pointer hits a plane mirror and the reflected ray strikes a screen. How far away from the point X should the ray strike the mirror to cause the reflected ray to hit point R?

• Q23 An observer O cannot see the image of target T through the mirror. What is the minimum distance he should move to see the image of target T through the mirror?

• 5

### Refraction - Names

• Q24 Which are the incident ray, the refracted ray and the emerging ray?

• Q25 Which are the angle of incidence and angle of refraction?

• Q26 A ray of light travels from air to water as shown below. What are ray AB and ray AC?

• 6

### Refraction - Angle of refraction, Snell's Law

• Q27 A ray of light travels from air to glass as shown below. Given that the refractive index of air is 1.0 and the refractive index of glass is 1.5, what is the angle of refraction, r?

• Q28 A ray of light travels from air to water as shown below. Given that the refractive index of air is 1.0, what is the refractive index of water?

• Q29 A ray of light travels from water to air as shown below. Given that the refractive index of air is 1.0 and the refractive index of water is 1.3, what is the angle of incidence, i?

• Q30 A ray of light travels from glass to air as shown below. Given that the refractive index of air is 1.0, what is the refractive index of glass?

• Q31 A ray of light travels from water to glass as shown below. Given that the refractive index of water is 1.3 and the refractive index of glass is 1.5, what is the angle of refraction?

• Q32 A ray of light travels from diamond to glass as shown below. Given that the refractive index of diamond is 2.0 and the refractive index of glass is 1.5, what is the angle of incidence?

• Q33 A ray of light travels from water to diamond as shown below. Given that the refractive index of water is 1.3, what is the refractive index of diamond?

• Q34 A ray of light travels from air to diamond as shown below. Given that the refractive index of air is 1.0 and the refractive index of diamond is 2.2, what are the angles ABD and EBC?

• Q35 A light ray travels from a medium P to medium Q. Given that medium P has a refractive index of 1.0 and medium Q has a refractive index of 1.2, which of the following is a possible refracted ray?

• Q36 A light ray travels from a medium P to medium Q. Given that medium P has a refractive index of 1.5 and medium Q has a refractive index of 1.0, which of the following is/are possible refracted ray(s)?

• Q37 A light ray passes through a rectangular glass block as shown in the diagram below. What is the refractive index of the glass?

• Q38 Which of the following minimize the gap x?

• 7

### Refraction - Critical angle and total internal reflection

• Q39 What is/are the condition(s) needed for total internal reflection to take place?

• Q40 A light ray travels from a medium P to medium Q. Given that medium P has a refractive index of 1.5 and medium Q has a refractive index of 1.2, which of the following rays is/are possible outcome(s)?

• Q41 A ray of light in a glass block is incident on a boundary with air at an angle of incidence of 40°. The critical angle at this boundary is 43°. What happens to the ray of light at the boundary?

• Q42 A periscope uses two 45° prisms to reflect the light ray into the observer’s eye. What is the possible refractive index of the prism material?

• Q43 Refraction takes place when light travels from medium A into air as shown. What is the critical angle for the situation below?

• 8

### Refraction - Light in multiple media

• Q44 A scientist is given 3 mediums to do a certain experiment. The refractive indices of the three mediums are 1.0, 1.2 and 1.4. What are the possible critical angles obtained by these three mediums?

• Q45 A light ray travels through three mediums as shown. Which of the following shows the ascending order of refractive index?

• Q45 explanation

• Q46 A light ray travels from medium 1 to 3 as shown. Which of the following is ascending order of refractive index?

• Q47 Light passes through three different mediums as shown in the diagram below. Which of the following statements is true?

• 9

### Refraction - Complex paths

• Q48 Which of the following is the emergent ray when the incident ray strikes the glass prism from air?

• Q48 explanation

• Q49 Which of the following is the emergent ray when the incident ray strikes the glass prism from air?

• Q49 explanation

• Q50 Which of the following is not the effect of refraction?

• 10

### Refraction - Apparent depth

• Q51 An air bubble is trapped 6 cm from the edge of a glass block as shown. Given that the refractive index of glass is 1.5, how far does the air bubble seem to be away from the observer when viewed from the position shown?

• Q52 A fish seems to be 6.0 cm below the water surface. Given that the refractive index of water is 1.4, what is the actual depth of the fish below the water?

• 11

### Lenses - Definitions

• Q53 Two light rays parallel to the principal axis strike a converging lens and converge to point B as shown. Which point is the focal point?

• Q54 The focal length is

• Q55 Which of the following does not affect the focal length of a convex lens?

• 12

### Lenses - Image characteristics

• Q56 When an object is placed 20 cm from a thin converging lens, a real image equal in size to the object is formed. The object is then moved 3 cm away from the lens. Which of the following describes the new image formed?

• Q57 Which of the following diagrams correctly shows the arrangement of a lamp, lens and film in a photographic enlarger?

• Q58 Which of the following are true?

• Q59 An object O is placed at the position shown. What are the characteristics of the image produced?

• Q60 An object O is placed at the position shown. What are the characteristics of the image produced?

• Q61 An object O is placed at the position shown. What are the characteristics of the image produced?

• Q62 An object O is placed at the position shown. What are the characteristics of the image produced?

• Q63 An object O is placed at the position shown. What are the characteristics of the image produced?

• Q64 Which of the following are always true?

• Q65 Which of the following is a virtual image?

• 13

### Lenses - Images and distances

• Q66 A converging lens has a focal length of 15 cm. Given that an object is placed 10 cm from the optical centre of the lens, what are the characteristics of the image formed?

• Q67 A converging lens has a focal length of 15 cm. Given that an object is placed 31 cm from the optical centre of the lens, what are the characteristics of the image formed?

• Q68 A converging lens has a focal length of 15 cm. Given that an object is placed 5 m from the optical centre of the lens, what are the characteristics of the image formed?

• Q69 When an object is placed 29 cm from the optical centre of the converging lens, the image formed is real, inverted and magnified but when the object is placed 31 cm from the optical centre of the lens, the image formed is real, inverted and diminished.

• Q70 An overhead projector in the classroom uses a converging lens to produce the image on the screen. If the focal length of the lens is 10 cm, where should a transparency be placed from the converging lens to form a clear image?

• Q70 explanation

• Q71 A camera uses a converging lens to produce an image on the film. If the focal length of the lens is 10 cm, where should an object be placed from the camera for photo taking?

• Q72 A telescope uses a converging lens to see birds which are far away. If the focal length of the lens is 20 cm, what is the distance from the observer’s eye to the lens to see a clear image of the bird?

• 14

### Lenses - Lens ray diagrams

• Q73 Which of the following are true?

• Q74 Which of the following objects can form the image I?

• Q75 An object O and its image I are shown below. Where is the position of the converging lens?

• Q76 An object O and its image I are shown below. Where is the position of the converging lens?

• Q77 A light ray parallel to the principal axis travels into a converging lens as shown. Which is the emergent ray from the converging lens?

• Q78 A light ray travels into a converging lens as shown. Which is the emergent ray from the converging lens?

• Q79 A light ray travels into a converging lens as shown. Which is the emergent ray from the converging lens?

• Q80 A light ray travels into a converging lens as shown. Which is the emergent ray from the converging lens?

• Q81 Which of the following shows how the light ray travels through a thick converging lens?

• Q81 explanation

• 15

### Lenses - Magnification

• Q82 A slide with an image 4 cm x 2 cm is placed at a distance of 10 cm behind a converging lens and a clear image is formed on a screen 1.1 m from the slide. The size of the image on the screen is

• Q82 explanation

• Q83 A converging lens is used to magnify a real image to three times its original size. Given that the object is placed 20 cm from the converging lens, what is the image distance?

• 16

### Lenses - Lens equation

• Q84 A converging lens has a focal length of 15 cm. Given that an object is placed 10 cm from the optical centre of the lens, what is the image distance (the distance from the image to the optical centre)?

• Q84 explanation

• Q85 A converging lens has a focal length of 20 cm. If an object is placed 50 cm from the optical centre of the lens, how far will the image be from the optical centre of the lens?

• Q85 explanation

• Q86 A converging lens has a focal length of 10 cm. If an object is placed 18 cm from the optical centre of the lens, how far will the image be from the optical centre of the lens?

• Q87 A converging lens has a focal length of 10 cm. If an object is placed 5 cm from the optical centre of the lens, how far from the optical centre of the lens will the virtual image appear?

• Q87 explanation

• Q88 In an experiment to determine the focal length of a converging lens, the object distance and the image distance recorded were 20 cm and 30 cm respectively. What is the focal length of the converging lens?

• Q89 A converging lens is used to magnify a real image to four times its original size. Given that the focal length of the converging lens is 20 cm, what is the object distance?

• Q90 A converging lens is used to magnify a virtual image to four times its original size. Given that the focal length of the converging lens is 20 cm, what is the object distance?

• 17

### Lenses - Diverging lens questions

• Q91 Which of the following emergent rays is correct when the incident ray strikes the diverging lens?

• Q92 Which of the following are true?

• Q93 The diagram below shows rays of light passing through an object X. What could X be?

• 18

### Structured Questions

• SQ1 (part 1) A lens and a close object definitions and ray diagram

• SQ1 (part 2) A lens and a close object real and virtual images

• SQ2 A lens and a distant image

• SQ3 (part 1) Lamp in a box focal length of lens

• SQ3 (part 2) Lamp in a box changing the mirror

• SQ4 Diverging lens

• SQ5 Bent fiber optic cable

• SQ6 Angle of entry for straight optical cable

• SQ7 (part 1) Light in air and water critical angle

• SQ7 (part 2) Light in air and water apparent depth