5.1 Understanding reflection of light.

A student is able to:

Describe the characteristic of the image formed by reflection of light State the laws of reflection of light Draw ray diagrams to show the position and characteristics of the image formed by a plane mirror, convex mirror and concave mirror Describe applications of reflection of light Solve problems involving reflection of light Construct a device based on the application of reflection of light

CHAPTER 5LIGHT

Learning Objective and Learning Outcomes

( …………. / 15 X 100% = ………………. % )

Fill in the blanks with the suitable terms:

1. The characteristics of image when light from an object is reflected by a plane mirror includes

(1)…………………… (inverted/ laterally inverted), same size, (2)………………(same distance/ difference distance) from the mirror at perpendicular line and virtual.

2. The Law of reflection of light states that

i) the angle of incidence equals (3)………………………….

ii) the incident ray, the reflected ray and (4)……………………. (normal line/principal axis) are all lie at the same plane.

3. (a) Complete the image of L in the diagram of reflection below.

(b) On the diagram above,i. Show the light ray direction and the normal line of the mirror. (5)ii. show the angle of incidence and label as i, the angle of reflection and label as r .(6)iii. show the distance of object, lo and distance of image li perpendicular to the mirror.(7)

4. When the parallel rays are directed to concave mirror, the reflected rays will meet at a point

before the mirror. It is called the (8)……………………. (vertex/focal point) of the concave mirror.

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Mirror

Observer’s eye

Light ray from object

5. When the parallel rays are directed to convex mirror, the reflected rays will (9)……………… (diverge/ converge). When the rays are extrapolated, it will meet at a point behind the mirror, it’s the focal point.

6. Diagram below shows three parallel rays are directed to a concave and a convex lens, draw the reflected rays and indicate the focal point, F in each case. Show the direction of reflected rays. Relate the relation between centre of curvature, C, with focal point, F, of a mirror.

(10) (11)

7. Convex mirror is often installed at the cornering of a hidden road and in the convenience store.

This mirror allows us to see wide angle of objects but the size of the image is (12)…………….. ( smaller/ magnified).

8. Diagram below shows a ray directed on a plane mirror. i) Uses a red / blue ink ball pen, draw the normal line and the reflected ray for the given incident ray (use protractor and ruler to assist you). ii) Now, using a pencil draw to show the mirror turned 10o clockwise. Thus, draw the new normal line and new reflected ray. Observe the changes of angle for the reflected ray.

(13)

9. When a mirror turns xo, the angle between the two rays (incident and reflected) will have a

change of (14)………………… (1x0/ 2x0/ 3x0).

10. Mirror is used in measuring instruments like ammeter, voltmeter and galvanometer. It is to help

the user to read accurately and avoid (15)………………….. (parallax error/systematic error).

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Learning Objective and Learning Outcomes

5.2 Understanding refraction of light.

A student is able to: Explain refraction of light

Define refractive index as

Determine the refractive index of a glass or Perspex block State the refractive index, , as Speed of light in a vacuum Speed of light in a medium Describe phenomena due to refraction Solve problems involving refraction of light

( …………. / 14 X 100% = ………………. % )

1. Light travels in a straight line, but when travels from one medium to another medium with different density, it changes direction. The change in direction when light ray travels from one medium to another medium is called (1)…………………(reflection / refraction)

2. The light ray that travels along the (2)………….. (normal/ tangent ) line of the boundary between

two medium does not bend.

3. When a light ray travels from an optically denser medium to a less dense medium, it refracts (3)……………… (far from / towards) the normal.

4. When a light ray travels from an optically less dense medium to a denser medium, the angle of incident ray (at less dense medium) is (4)………………. (small/ larger) then the angle of refracted ray (at denser medium).

5. In the diagram below, a. draw two normal lines of the ray to and from the glass blockb. show the refracted light of the glass blockc. complete the direction of lightd. indicate the angle of incident, , and the angle of refraction, .

(5)

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6. Angle of incident or angle of refraction is an angle made between the ray and the (6)……………. (normal line/ surface medium).

7. (7)………………(Light Law/ Snell’s Law) says that the ratio of is a constant. It is known as the

(8)……………….(reflective/ refractive) index of a medium.

8. The speed of light (9)…………..….(increases/ decreases) as it travel into a high medium, therefore

the refractive index of a medium n = , simplified n = .

9. Due to refraction of light, (i) A straight straw / rod appears (10)………… (bending /without bending) at the boundary of

liquid.

(ii) The bottom of a pool liquid appears (11)………… (deeper / shallower) than the actually depth.

10. The (12)…………………(refractive/ reflective) index of liquid can be calculated using,

n = simplified n = .

11. In the diagram below use the following steps to construct the refraction of light of a coin in a beaker of water.a. draw the two normal lines at the boundary of liquidb. draw and show the two rays refracted at the air (further from normal line)c. draw an eye at the correct positiond. from the eye, followed the refracted rays, extra-polated dotted lines backward and meet above the original coin. Draw a dotted oval shape,

to represents the image of the coin.

(13)

12. The (14)…………………... (phenomenon/application) of refraction of light include mirage, sunrise, sunset, twinkling stars at night and wriggling of distant objects on hot day.

Learning Objective and Learning Outcomes

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5.3 Understanding total internal reflection of light.

A student is able to: Explain total internal reflection of light Define critical angle (c)

Relate the critical angle to the refractive index i.e

Describe natural phenomenon involving total internal reflection

Describe applications of total internal reflection Solve problems involving total internal reflection

( …………. / 13 X 100% = ………………. % )

1. (a) Diagram below shows a light ray travels through a semicircle glass block. If the angle, of incident is small, most of the light is (1)…………..(separation/ refracted) but some is reflected.

(b) Label in the diagram i) the refracted light and reflected light. (2)

ii) the angle of incident, and angle of refraction, r. (3)

2. The critical angle, c is the incident angle, when the maximum refraction occurs at r = (4)………. (90 o/1800). On the diagram below, label the critical angle, c (5) and refraction angle, r (6).

3. The total internal reflection occurs when,(a) i) Light travels from a (7)……………………………( less dense medium to a denser medium /

denser medium to a less dense medium), and ii) When the incident angle, is (8)………(less/ greater) than the critical angle, c. (b) Name the phenomena occurs in the diagram below (9)…………………………… (reflection/

total internal reflection)

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4. Another formula of refractive index, n =

5. The phenomenon of total internal reflection of lights includes mirage in the desert, mirage on hot afternoon on highway and(10)………….. (rainbow/ echo).

6. During hot day, the air on the ground is less dense compare with cold air at higher level . When the incident ray is greater than the critical angle, total internal reflection occurs. Light from the sky is refracted further away from normal line gradually because the density of air decreases gradually. Our eye sight sees image as though there is water drops on the ground.

Name the natural phenomenon (11)…………………………… ( rainbow/ echo/ mirage).

7. Refers to the diagram given below: i) Complete the ray diagram of mirage beginning from the object to point A.(12) iii) Show how we can see the pool of water (mirage) on the highway. (13)

incident raynormal line denser layer

Eye

A

Less dense

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Object

Image Pool of water appears at the highway on a very hot day.

Learning Objective and Learning Outcomes

5.4 Understanding lenses.

A student is able to: Explain focal point and focal length Determine the focal point and focal length of a convex lens and

concave lens Draw ray diagrams to show the positions and characteristics of

the images formed by a convex lens and concave lens.

Define magnification as

Relate focal length (f) to the object distance (u) and image

distance (v) i.e.

Describe, with the aid of ray diagrams, the use of lenses in optical devices.

Construct an optical device that uses lenses. Solve problems involving to lenses.

( …………. / 30 X 100% = ………………. % )

1. When light passes through a convex lens, the light (1)……………(diverge/ converges) to a point and we call it (2) …………….(object distance/ focal point). Convex lens is also known as a converging lens.

2. Concave lens is also known as a (3)……………..(converging/ diverging) lens because light passes through it diverges from the focal point, F.

3. For the ray diagram below fill in the following labels: Principle axis, P (4), Optical centre, O (5), Focal point, F (6), focal length, f (7).

4. Complete the following ray diagrams to find out the images of each situation of an object. Given the characteristics of images includes real or virtual, upright or inverted, diminished / smaller, same or magnified or larger. State the characteristics for each situation.

a) (8)

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● ●● ●

Characteristics of image:i (9)……..…...

ii (10)………..

iii(11)………...

Object

b) (12)

c) (16)

5. (a) When the object is too near from the convex lens, the image is virtual, magnified and upright.(b) Concave lens produce only one type of image that is virtual, diminished and upright.

Base on the two statements above, draw the images for the following diagrams.(i) (20) (ii) (21)

6. Complete the following ray diagram and name the characteristics for each.

(22) (23)

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● ●● ●

● ●● ●

Characteristics of image:

i (13)….……..

ii (14).……….

iii (15).………

Characteristics of image:

i (17)…….…...

ii (18)………..

iii(19).……….

● ● ● ●

● ● ● ●

Characteristics of image: (24)………,……………., ………………

Characteristics of image: (25)………,………….., ……………….

Object

Object

Object

Object Object

7. The symbol for image distance is (26)…….(v/u/f) and the symbol for object distance is (27)…... (v/u/f).

8. The formula for magnification m = or m =

9. Given the formula can be used to solve optical problems. Connect the sign convention

and its meaning.

Sign convention Meaning

f is positive image is real

(28) f is negative convex lens

(29) v is negative image is virtual

(30) v is positive concave lens

______________Question End_____________

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