D. Long answer questions,
1. What is light? How does it help us to see an object?
2. What is a shadow? What are the essential things required to form a shadow of an object?
3. Does the size of the shadow of an object depend upon the size of the object? How does the size
of a shadow vary with the distance between a light source and the object?
4. How did people in earlier times use shadows of objects in the sunlight to measure time?
5. Describe an activity to show that light travels in a straight line.
6. What is the difference between an image and a shadow? Does a pinhole camera produce an image
or a shadow of the object?
Answers
Answer:
1) Light is a form of energy that helps us to see objects.
explanation: when ever light falls on an object it gets reflected from the surface of that object and strikes in our eyes hence creating an image of that in our eyes, in this way light helps us to see an object. without this process of reflection no object can be seen. so here reflected ray from surface plays the major role in helping us to see an object.
2)When light fall son an opaque object, light is obstructed and a dark patch on a screen kept behind is called shadow. This is because light propagates in straight line. If distance between object and screen is less, the shadow will be (umbra) dark and smaller. If the distance is increased shadow will be dim and larger. Conditions Required for a shadow to form are: 1. There should be a source of light. 2. An opaque object. 3. A screen.