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Chapter: Light
Very Short Questions
1.
What is light?
Light is a form of energy that gives the sensation of vision.
2.
How does light travel?
Light travels in a straight line.
3.
Name a common source of light.
A common source of light is the Sun.
4.
Is light a form of energy?
Yes, light is a form of energy.
5.
What is light absorption?
Light absorption is the process in which an object takes in the light that
falls on it instead of reflecting or passing it through.
6.
What is rectilinear propagation of light?
Rectilinear propagation of light is the property of light by which it
travels in a straight line.
7.
Does light travel in straight lines?
Yes, light travels in straight lines.
8.
What is a ray of light?
A ray of light is a thin line that represents the path along which light
travels.
9.
What is a pinhole camera?
A pinhole camera is a simple camera without a lens that uses a tiny hole to
capture images.
10. What
is a shadow?
A shadow is a dark area or shape that forms when an object blocks light
from a source.
11. What
are two types of shadow?
The two types of shadow are umbra and penumbra.
Short questions
1.
Give two examples of natural sources of
light.
The two examples of natural sources of light are the Sun and a firefly.
2.
Does light need a medium to travel
through?
No, light does not need a medium to travel through.
3.
Explain why we are able to see objects
that emit light and objects that reflect light.
We are able to see objects that emit light because they produce their own
light, which enters our eyes. We are able to see objects that reflect light
because they bounce light from another source into our eyes.
4.
What are some common objects that reflect
light?
Some common objects that reflect light are mirrors, water, metals and
glass.
5.
What is meant by transparent materials?
Give two examples.
Transparent materials are materials that allow light to pass through them
completely. For example, clean water and glass.
6.
Name a translucent material and explain
how light passes through it.
Frosted glass is an example of translucent material. When light passes
through frosted glass, it is scattered in different directions. This scattering
of light makes objects on the other side appear blurry or unclear.
7.
What happens when light is absorbed by an
object? Give an example.
When light is absorbed by an object, the light energy is taken in by the
object and usually changes into heat energy. For example, a black shirt absorbs
more sunlight and becomes warmer than a white shirt.
8.
Describe rectilinear propagation of light
and why it is important.
Rectilinear propagation of light is the property of light by which it
travels in a straight line. It is important because it helps us understand the
formation of shadows and the working of a pinhole camera.
9.
Not necessary
10. What
happens to the image formed in a pinhole camera if the hole is made larger?
When the hole is made larger in a pinhole camera, the image becomes
brighter but blurred.
11. Can
a pinhole camera capture color images? Why or why not?
Yes, a pinhole camera can capture color images if a color-sensitive film or
sensor is used. The pinhole only lets light in, so the color of the image
depends on the type of film or sensor placed inside the camera.
12. How
is a shadow formed? What factors can affect the size and shape of a shadow?
A shadow is formed when an opaque object blocks light from reaching a
surface. The factors that can affect the size and shape of a shadow are:
i) Distance between the light source, object and surface
ii) Position or angle of the light source
iii) Size and shape of the object
13. What
is a sundial and how does it work?
A sundial is a device used to tell time using sunlight. It has a stick,
called a gnomon, that casts a shadow on a marked surface called the dial. As
the Sun moves across the sky, the shadow moves, showing the time of day.
14. Explain
how the position of the sun affects the shadow cast by a sundial.
The position of the sun changes throughout the day, causing the shadow on a
sundial to change its direction and length. In the morning the shadow is long
and points west, at noon it is shortest, and in the evening, it becomes long
again and points east.
15. How
can a sundial be used to tell time accurately?
To use a sundial accurately, it must be properly placed and the gnomon must
point toward the North in the Northern Hemisphere and toward the South in the
Southern Hemisphere.
Long questions
1.
Not necessary
2.
Not necessary
3.
Identify the given objects and state
whether they are luminous objects or non-luminous objects. Also, write reason
to justify your answer.
a. Lantern b. Moon c. Light bulb d. Book
The lantern and light bulb are luminous objects because they produce their own
light. The Moon and book are non-luminous objects because they do not produce
their own light but reflect light from other sources.
4.
Not necessary
5.
Differentiate between:
a. Ray and beam of light
|
Ray
of Light |
Beam of Light |
|
A ray of
light is a thin line that represents the path along which light travels. |
A beam of
light is a collection of rays traveling together. |
|
It is
represented by a straight line with an arrowhead. |
It is represented
by a group of straight lines with arrowheads. |
b. Umbra
and penumbra
|
Umbra |
Penumbra |
|
Umbra is the
fully dark region of a shadow where no light reaches. |
Penumbra is
the partially lighted region of a shadow where some light reaches. |
|
It forms a
sharp and darker shadow. |
It forms a
lighter and blurred shadow. |
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