Light
ASSIGNMENT
1. Fill in the blank spaces, by choosing the correct words from the list given below :
List : large, high, moon, umbra, light, camera, transparent, straight, pass, curvature,
convex, shaving, object, enlarged, behind, concave, infinity, principal focus, area,
sphere
(i) The bodies which give ......................... energy of their own, are called luminous
bodies.
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(ii) A ..................... body allows most of the light energy to ................... through it.
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(iii) A pin hole ......................... is based on the principle that light travels in
......................... lines.
(iv) The shadow cast by earth is very ......................... and can completely cover the
whole of ......................... during lunar eclipse.
(v) Birds flying very ......................... do not cast their shadows, as .........................
finishes in air.
(vi) The centre of the hollow ............................. of which the spherical mirror is a part,
is called centre of ............................. .
(vii) Drivers prefer ...................... mirror because it forms an erect, diminished and virtual
image close to the eye and covers a wide ........................... of road behind them.
(viii) Concave mirror is used as ......................... mirror because it forms ...........................
erect and virtual image.
(ix) Image in a plane mirror is as far ............................. as the ............................. is in
front of it.
(x) A real, inverted and diminished image is formed in ............................. mirror, when
the object is in between ............................. and the centre of curvature.
(xi) An image diminished to a point and virtual and erect in nature, is formed by
convex mirror, when object is situated at ............................. .
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2. Write ‘T’ for true and ‘F’ for false in front of the following statements :
(i) The image formed in a pinhole camera, is always erect.
(ii) Light is an invisible energy which causes in us the sensation of vision.
(iii) A bird flying high in the sky does not cast its shadow on ground.
(iv) Moon is a luminous body in the sky.
(v) The size of image in the pinhole camera increases, if the object is moved towards
pinhole.
(vi) The light produced by a bulb is called shadowless light.
(vii) Convex mirror always forms a virtual image.
(viii) Concave mirror always forms a real image.
(ix) Pole is the centre of sphere of which spherical mirror is a part.
(x) In case of plane mirror, the image is of same size as the object.
(xi) Any ray of light passing through the centre of curvature after reflection retraces its
path.
(xii) Concave mirrors are used as reflectors for street lights.
(xiii) Plane mirror is a better rear-view mirror, as compared to convex mirror.
(xiv) Concave mirror is used as shaving mirror, because it makes a better shave.
(xv) Dentists use concave mirror, because it is curved and fits well behind teeth.
(xvi) When an object is at infinity, the rays coming from it, are always
parallel.
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3. Statements given below are incorrect. Write the correct statements.
(i) A region of total darkness is called penumbra.
(ii) The image formed by a plane mirror is always inverted.
(iii) Pole of a spherical mirror is the centre of curvature of the mirror.
(iv) Solar eclipse is caused when the sun, the earth and the moon come in straight line,
such that the earth is in the middle.
(v) The image formed by a pinhole camera is always virtual, erect and diminished.
(vi) Plane mirror is employed as rear-view mirror in automobiles.
(vii) Two convex mirrors are employed in the construction of a periscope.
(viii) When a ray of light strikes a plane mirror perpendicularly, the angle of incidence
is 90°.
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(ix) A concave mirror forms a virtual image, when an object is between F and C.
(x) A plane mirror can focus solar rays to a point.
4. Match the statements in column A, with those in column B :
Column A
Column B
(i) Distance between the pole and the principal
focus of a convex mirror.
Solar eclipse
(ii) Distance between the pole and centre of
curvature of a convex mirror.
Focal length
Z
B
(iii) A device used for seeing, over the heads of
crowds.
(iv) A mirror used in the solar cookers.
Plane mirror
Periscope
(v) A spherical mirror used as a shaving mirror.
(vi) A spherical mirror used as a rear-view mirror.
Convex mirror
Regular reflection
(vii) A reflection in which reflected rays travel as
parallel beam.
Diffused reflection
(viii) A reflection taking place from the walls of a
building
Concave mirror
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(ix) An eclipse formed on the full moon night.
(x) An eclipse formed on the new moon day.
Radius of curvature
Lunar eclipse
5. Tick (
) the most appropriate answer.
(i) A region of total darkness, is called :
(a) penumbra
(b)
(c) shadow
(d)
(ii) A ray of light travelling towards a polished
(a) normal
(b)
(c) incident ray
(d)
umbra
none of these
surface is called :
reflected ray
none of these
(iii) Image formed in a concave mirror is always :
(a) inverted
(b) erect
(c) some times inverted and some times erect
(d) none of these
(iv) A medium which almost completely allows the light to pass through them, is
called :
(a) homogeneous medium
(b) hetrogeneous medium
(c) translucent medium
(d) transparent medium
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(v) The image formed by a convex mirror is always :
(a) real
(b) inverted
(c) enlarged
(d) diminished
(vi) The image formed by a plane mirror is always :
(a) erect
(b) inverted
(c) diminished
(d) enlarged
(vii) The mirrors used in a periscope are :
(a) plane
(b) convex
(c) concave
(d) none of these
(viii) The mirror used as a rear-view mirror, in automobiles, is :
(a) plane
(b) convex
(c) concave
(d) none of these
(ix) The mid point of a spherical mirror, is called :
(a) aperture
(b) centre of curvature
(c) pole
(d) principal focus
(x) When the angle of incidence is zero, the rays of light strikes a plane
mirror at an angle of :
(a) zero degree
(b) 90°
(c) 45°
(d) none of these.
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6. Find the odd one out. Give a reason for your choice.
(a) For a plane mirror, the image is always :
(i) real,
(ii) erect,
(iii) same size as the object,
(iv) formed as far behind the mirror as the object is in front of it.
(b) For a convex mirror, the image is always :
(i) virtual,
(ii) magnified,
(iii) erect,
(iv) formed behind the mirror.
(c) For a concave mirror, the image when object is between P and F, is always :
(i) virtual
(ii) erect,
(iii) magnified/diminished,
(iv) formed in front of the mirror.
7. (i) What is light?
(ii) By giving four examples each, define the following :
(a) Luminous bodies
(b) Non-luminous bodies
8. Pick out the luminous and non-luminous bodies from the list given below :
(i) a lighted cigarette, (ii) marble, (iii) dial of watch, (iv) sun, (v) fire flies,
(vi) diamond, (vii) red hot iron, (viii) bicycle, (ix) trees, (x) a radio set.
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9. By giving at least four examples each, define the following terms :
(i) Heterogeneous medium
(ii) Transparent medium
(iii) Opaque bodies
(iv) Translucent bodies
(v) Homogeneous medium
10. What do you understand by the following terms? Support your answer by drawing a
diagram.
(i) Ray of light
(ii) Convergent beam of light
(iii) Divergent beam of light
(iv) Parallel beam of light
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11. Draw a neat and labelled diagram to show that light travels in straight lines.
12. (i) What is a shadow?
(ii) Name and define two kinds of shadows.
(iii) State three conditions for the formation of shadow.
13. Show the formation of shadows in Figs. 1 and 2 :
14. By drawing a neat and labelled diagram, show, why flying birds do not cast their
shadows. Explain briefly your answer.
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15. (i) In the space provided below, are shown the sun, the moon and the earth. Complete
a ray diagram to show the formation of eclipse.
(ii) Name the eclipse illustrated by the diagram.
(iii) On which day does this eclipse take place?
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(iv) Why does this eclipse last for a very short interval of time? Explain.
16. (i) Draw a neat and labelled diagram of lunar eclipse.
(ii) Answer the following questions :
(a) On which day does lunar eclipse take place?
(b) Why is lunar eclipse generally total?
(c) Why is lunar eclipse a frequent phenomenon?
17. (i) What is the principle of pinhole camera?
(ii) Why is the interior of pinhole camera blackened?
(iii) State three characteristics of an image formed by a pinhole camera.
(iv) How the image formed in a pinhole camera affected, when :
(a) Distance between the pinhole and the screen increases?
(b) Distance between the pinhole and the screen decreases?
18. (i) What do you understand by the term reflection of light?
(ii) By drawing diagrams, define :
(a) Regular reflection
(b) Diffused reflection
(iii) State one use each of :
(a) Regular reflection
(b) Diffused reflection
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(iv) Name four substances, in each case, which cause :
(a) Regular reflection
(b) Diffused reflection
19. Define the following terms with reference to the reflection of light :
(i) Mirror
(ii) Incident ray
(iii) Reflected ray
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(iv) Normal
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(v) Angle of incidence
(vi) Angle of reflection
(vii) Point of incidence
20. State two laws of reflection.
21. (i) What do you understand by the following terms?
(a) Real image
(b) Virtual image
(ii) Name the kind of image (real or virtual) formed in case of plane mirror.
22. State four characteristics of an image formed in a plane mirror.
23. (i) A monkey sits at a distance of 4 m from a plane mirror. How much is the distance
between the monkey and its image?
(ii) If the monkey moves 1 m towards mirror, how much is the distance between the
monkey and its image?
24. Give four practical uses of plane mirrors, other than periscope.
25. What is a reflecting periscope?
26. Define the following terms used for spherical mirrors :
(i) Concave mirror
(ii) Convex mirror
(iii) Pole
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(iv)
(v)
(vi)
(vii)
(viii)
(ix)
Centre of curvature
Principal axis
Radius of curvature
Principal focus of concave mirror
Principal focus of convex mirror
Focal length
27. (i) State three rules for drawing images in case of convex mirror.
(ii) State three rules for drawing images in case of concave mirror.
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28.
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Trace the course of reflected rays in figure (a) and figure (b) and in each case, mark
principal focus.
29.
The above diagram shows an object AB placed in front of a concave mirror. By drawing
two-rays diagram, locate the position of image and state three characteristics of the
image.
30. (i) Give three uses of concave mirrors.
(ii) Give two uses of convex mirrors.
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