question in optics

(A) Basic Concepts of Light
1. What is light a form of?
?? A form of energy.
2. In what form does light energy travel from the Sun?
?? In the form of waves.
3(a) Does light need a medium for travelling?
?? No.
(b) Thus, can light travel in a vacuum?
?? Yes.
Comments:
? Vacuum is “empty space”. It does not contain matter.
? Evidence that light can travel through vacuum:
o Sunlight reaching the Earth, even though most of the space between the Sun
and Earth has no matter.
4. Fill in the blanks:
(a) Light travels in ________ lines.
?? straight
(b) The path along which light travels is called a ________.
?? ray
(c) ________ are drawn on light rays to show the direction in which light travels.
?? Arrows
(d) A ________of light consists of a bundle of light rays.
?? beam
5. State the speed of light in vacuum.
?? 3 x 108 m/s
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(A1) Light Vs Nature of Surface
6. State the three effects that light experiences when it falls on a surface.
?? When light falls on a surface, it can be:
I. Reflected
II. Transmitted / Refracted
III. Absorbed
Comments:
? Examples of the above:
o When light falls on mirror ?? Light will be reflected. (I.e. light “bounces” back).
o When light falls on glass ?? Light will be transmitted. (I.e. light passes through it.)
o When light falls on wood ?? Light will be absorbed.
? Our focus in this chapter will be on effects I (reflection) and II (refraction).
7. What is the factor that will determine whether light is absorbed, transmitted or reflected
when it falls on a surface?
?? The nature of the surface that light falls on.
8. Give two examples each of
(a) Rough and dull surfaces
?? Black curtains
?? Paperboards
(b) Smooth and shiny surfaces
?? Mirrors
?? Polished metals
(A2) Regular Vs Diffused Reflection
9. The nature of surfaces can determine the type of reflection. State the type of surface that
results in regular reflection and diffused (or irregular) reflection.
?? Smooth and shiny surfaces result in regular reflection.
?? Rough and dull surfaces result in diffused (or irregular) reflection.
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10(a) Distinguish between regular and diffused reflection.
?? In regular reflection, parallel light rays remain parallel after falling on a smooth and
polished surface.
?? In contrast, in diffused reflection, parallel light rays are scattered in different
directions after falling on a rough surface.
(b) Draw diagrams to illustrate
(i) Regular reflection,
?? Answer:
(ii)