S1 SCI CHAP 5 RAY MODEL OF LIGHT

Question 1

Which of the following statements is not true about the mirror image of an object?

A: If the object moves further from the mirror, the image will appear further from the mirror.
B: The mirror image is real
C: The image is laterally inverted
D: The mirror image cannot be captured on a screen

Answer 1

B

Question 2

Order the following media in terms of the speed of light from slowest to fastest: Glass, water, air

Answer 2

SLOWEST ——–> FASTEST
glass, water, air

Question 3

Which best explains why we are able to see non-luminous and opaque objects?

A: They are able to absorb the light rays and release them slowly so that we are able to see them.
B: They are able to bounce the light off their surfaces.
C: They are able to give out light on their own.
D: They are able to reflect the light rays so that the light rays can enter our eyes.

Answer 3

D

Question 4

Definition of reflection.

Answer 4

Reflection is the bouncing of light off a surface

Question 5

What is the first law of reflection?

Answer 5

The first law of reflection states that the incident ray, reflected ray, and the normal at the point of incidence all lie in the same plane (s-dimensional surface).

Question 6

What is the second law of reflection?

Answer 6

The second law of reflection states that the angle of incidence is equal to the angle of reflection.

Question 7

Characteristics of an image formed by a plane mirror. (5)

Answer 7

1. The image is of the same size as the object.
2. The image is upright.
3. The image is virtual.
4. The image is laterally inverted.
5. The perpendicular distance between the image and the mirror is equal to the perpendicular distance between the object and the mirror.

Question 8

What is the difference between a virtual and a real image?

Answer 8

A real image can be formed on a screen, whereas a virtual image cannot be formed on a screen.

Question 9

Applications of plane mirrors

Answer 9

1. Optical testing for eyesight: to reduce the distance required for optical testing.
2. Instrument scales: To avoid parallax errors.
3. To check our appearance.
4. Periscope: To see things across obstacles.

Question 10

Characteristics of convex mirrors

Answer 10

They have a surface that bends outwards and are also called diverging mirrors.
They cover a wider field of vision and form virtual, upright, diminished images. The image formed on the mirror is smaller than the object.

Question 11

Characteristics of concave mirrors

Answer 11

They have a surface that bends inwards and are also called converging mirrors. They also form virtual, upright, and magnified images.

Question 12

Applications of concave mirrors

Answer 12

1. Dentist’s mirror: to form a magnified image of the teeth.
2. Torchlight/headlights of a car: to reflect the light from the bulbs in the headlights to form strong beams of light.
3. At the base of a microscope: to reflect light from the lamp of a microscope to a specimen.

Question 13

Applications of convex mirrors

Answer 13

1. Rear-view mirrors of cars: to enable drivers to see a large area of the traffic behind them.
2. Security mirror: To allow shopkeepers to see a large area of the shop from a single location.
3. Blind corner mirrors: to allow drivers to see around blind corners at road junctions.

Question 14

Characteristics of an irregular/diffused reflection

Answer 14

Irregular/diffused reflection occurs on rough surfaces like white paper and clothes. Light rays are reflected in different directions.

Question 14

Characteristics of a regular reflection

Answer 14

Regular reflection occurs on smooth surfaces like a highly polished metallic surface, a calm surface of a water body, and a plane mirror. Light rays are reflected in the same direction.

Question 14

Why does refraction occur?

Answer 14

Light travels at different speeds in different transparent mediums. When light travels from air to water, its speed slows down. This change in speed causes the light ray to bend.

Question 14

The physical property of an optical medium.

Answer 14

An optical medium has a physical property called optical density that affects the speed at which light travels through the medium.

Question 15

Definition of refraction.

Answer 15

Refraction is the bending of light at the boundary between two different optical mediums due to a change in the speed of light as it passes from one material into the other.

Question 15

How does light bend from one optical medium to another?

Answer 15

Light bends towards the normal as it travels from an optically less dense medium to an optically denser medium.

Light bends away from the normal as it travels from an optically denser medium to an optically less dense medium.

Question 16

What are some effects of refraction?

Answer 16

1. Bending effects: A pencil appears bent when in water.
2. Actual vs perceived depth: A swimming pool appears shallower than it actually is.

Question 17

Describe what happens when a ray of light passes through a prism.

Answer 17

When a beam of white light travels through a glass prism, it is split into different colours.

Question 18

Why does dispersion of light take place as a ray of light passes through a prism?

Answer 18

Different colours of light slow down by different amounts. Hence, different colours of light bend towards and away from the normal through different angles.

Question 19

Name some applications of infrared radiation and describe how they are used.

Answer 19

Digital ear thermometers, remote controls, and thermal imaging cameras.

Thermal imaging cameras are used at airports, public buildings and offices to screen large groups of people quickly and accurately. They detect the amount of infrared emitted by a person and display images that re coloured to indicate the body temp of the person.

Question 19

What are the harmful effects of infrared radiation?

Answer 19

Workers who are exposed to infrared radiation for a long period of time must wear goggles to protect their eyes as part of their safety equipment as it can cause irritation. Infrared radiation trapped in the atmosphere also contributes to climate change.

Question 20

Name the radiations a part of the visible spectrum in the EM (electromagnetic spectrum)

Answer 20

Infra-red, light, ultraviolet radiation.

Question 21

Name some applications of ultraviolet radiation and describe how they are used.

Answer 21

UV radiation helps our body to make vitamin D. UV radiation is also used to treat certain medical conditions such as jaundice by exposing babies with jaundice to a controlled amount of UV radiation. UV radiation is also used to sterilise medical instruments, equipment, food, and water.

Question 22

What are the harmful effects of UV radiation?

Answer 22

Overexposure to UV radiation can harm our eyes and cause skin cancer.

Question 23

Name some applications of visible light and describe how they are used.

Answer 23

During the daytime, plants use the energy provided by visible light to make sugar from carbon dioxide and water through photosynthesis. We also make use of light as it allows us to see. It illuminates our surroundings at night as well.

Question 24

What are the harmful effects of visible light?

Answer 24

Visible light can cause some materials to undergo chemical changes and deteriorate. Some museums disallow flash photography and store old documents, photography, and paintings in the dark to protect them from being discoloured by light. Another harmful effect is light pollution, where there is excessive and inappropriate use of artificial light. Light pollution negatively impacts living things that depend on the Earth’s cycle of day and night to carry out life-sustaining activities. Artificial lights disrupt the migration of birds causing them to migrate too earl or too late. This can be fatal to the birds as they miss the ideal climate conditions for nesting and having an adequate supply of food. Another drawback is that large amounts of energy are wasted when too many lights are used.

Question 25

(no ans) NOTE: The following LOs may be used in context in assessments:

1. Show an awareness that EM radiation (e.g. infrared, ultraviolet, light) has both beneficial and harmful effects. (Note: the word ‘electromagnetic’ is not required)
2. Show an awareness about the impact of light produced by technology, on society and the environment (e.g. city lights can improve night visibility but cause light pollution, disorientation of birds, and use up a lot of electrical energy)

Question 26

Please please please remember how to draw a periscope light diagram T^T

Answer 26

https://www.pinterest.com/pin/1147925392518408099/

Question 27

Which of the following does not make use of reflection?

A. magnifying glass.
B. Dentist mirror.
C. submarine periscope.
D. blind corner mirror.

Answer 27

A

Question 28

NOTE: do not write “larger field of vision” write “wider field of vision”