## Reflection at curved surfaces and spherical surfaces Questions

1.  (a) The table below shows the object distance u and the corresponding image distance v of an

object placed in front of a convex lens.

 u cm 20 25 30 40 50 70 v cm 20 16.7 15 13.3 12.5 ecolebooks.com 11.5 1 cm-1u 1 cm-1V

(ii) Plot a graph of 1 (y axis) against 1

v u

(iii) From the graph, determine the focal length of the lens.

(b) State any two differences between human eye and the camera.

2.  A battery is rated 120 AH. How long will it work if it steadily supplies a current of 4A.

3.  a) Distinguish between mechanical and electromagnetic waves b) What is the relationship between periodic time and the frequency of a progressive wave

c) Complete the diagram below to show the shape of the wave fronts after passing the gap

4.  Complete the ray diagram to show the position of the image

5.  The figure below shows two mirrors inclined at an angle of 30o to each other. A ray of light is incident on one mirror as shown

Sketch the path of the ray to show its reflection on the two mirrors

6.  What is meant by the term spherical aberration?

7.  Complete the ray diagram below by showing the position of the image

State one application of the set up above

8.  A plain sheet of paper and a plane mirror both reflect light yet only the plane mirror forms

images. Explain why the paper cannot form images.

9.  Give one advantage and one disadvantage of using a convex mirror as a driving mirror

10.  The table below shows the image distance V and the corresponding magnification, M for an  object  placed in front of a concave mirror.

 Magnification M 0.5 1 2 3 4 5 6 Image distance V(cm) 15 20 30 40 50 60 70

(a) Plot a graph of V (y-axis) against the magnification M

(b) From the graph, determine the focal length of the mirror

(c) Given the image IM, locate the position of the object OB. Use arrows to show how

the image is formed on a concave mirror

11.  State the difference between a virtual image formed by a plane mirror and that formed by

a concave mirror

12.  Figure 1 shows an object O being viewed using two inclined mirrors M1 and M2. Complete

the diagram by sketching rays to show the position of the image as seen by the eye -E

13.  The figure below shows an object placed in front of a plane mirror. Draw appropriate rays to

locate the image as seen by the observer.

14.  Define the following terms as used in curved mirrors:-

(i) Principal focus (F)

(ii) Focal length  (f)

(b) By use of a ray; diagram, show how a concave mirror may be a dentist mirror

(c) An object is placed 12cm from a convex mirror of radius of curvature 20cm. Calculate

the position of the image

(d) (i) A lady holds a large concave mirror of focal length 1.8m from her face. State two

characteristics of her image in the mirror

(ii) A boy is standing between two cliffs A and B but nearer to cliff A than B. He stands 160m

from wall BA and shouts once. He hears two echoes and discovers that the time between the

two echoes is 0.8 seconds. Determine how far the boy is standing from cliff B given that the     speed of sound in air is 340m/s

## Reflection at curved surfaces and spherical surfaces Answers

1.  a) i)

 1u 0.05 0.04 0.033 0.025 0.02 0.014 1v 0.05 0.06 0.67 0.75 0.08 0.086

Any 4 correct values = 1 mk

Total = 3 mks

iii) ₤ = 10 + 1 cm

Any intercept = 1 mk

Rec. – 1 mk

Arrange of Reciprocal – 1 mk

b) – Focal length of eye lens is variable while that of camera is fixed. 1 mk]

– Eye has constant image distance. 1 mk

2.  120 = 4t

t = 120
1 mk

4

= 30 hrs 1 mk

3.  a) Mechanical waves – require medium for propagation

Electromagnetic can even travel in a vacuum (No medium required)

b) Frequency = 1/periodic time

c)

Extrapolation of light rays backwards

Dotted and upright change formed between C and F

5.  Reflected rays shown by arrow pointed correctly

angles marked as

i= r = 30o and i = r = 0 (implied), tar

6.  Spherical aberration is a situation where rays parallel but far away (distant) from the principal axis of a concave mirrors fails to pass through its focal point owing to the large radius of curvature of the mirror

7.  Complete the ray diagram below by showing the position of the image.

-It is used as a simple microscope or magnifying glass in the laboratory.

8.   – The reflection is a sheet of paper is irregular hence rays interfere with formation of images

– Reflection in a plane mirror is regular

9.  Advantage: wide field of vision

Disadvantages: Gives a wrong impression of the position of image due to the diminished

image formed

10.

Axes

Scale

Plotting all values

Plotting at least 5pts

Line

Magnification M

(b) From the graph

V = mf + f

f = V – intercept

= 10cm

OR

= 50 – 20

4 – 1

= 30

3

= 10cm

Correct rays with arrows

Object between P and F

11.  Image formed by concave mirror is enlarged while that formed by plane mirror is same

size as object

12.

1 for real ray

1 mk for virtual image

14.  (a) (i) Point on the principal axis to which all rays originally close and parallel to the

principal axis passes after reflection.

(ii) Focal length (f) – distance between the pole of the mirror (centre of the mirror) and the

principal focus f

(b)

(c) (i) u = +12cm, f = +10cm, V=?

1/f = 1/u + 1/V , 1/101/12 = 1/V

12 – 10 = 2

120 120

 V = 120 = 60cm

2

Image distance = 60cm

(d) (i) Enlarged, virtual, upright(any two)

(d) (ii)

2x – 320 = 0.8

340 340

2x – 0.94 = 0.8

340

2x = 1.74

340

2x = 591.6

x = 295.8M

Let the distance between the boy and the cliff be X and speed of sound in air is 340m/s

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