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CBSE Sample Paper Class 7 Science Light
Chapter 15 : Light
Multiple choice questions: (marks:1×2)
1.) Assertion (A) : A convex lens is called a converging lens.
Reason (R ) : A convex lens converges the light (bends inwards) which generally falls on it.
a.) Both A and R are true and R is the correct explanation of A.
b.) Both A and R are true but R is not the correct explanation of A.
c.) A is true but R is false.
d.) R is true but A is false.
Ans: Both A and R are true and R is the correct explanation of A.
2.) Assertion ( A) : A concave lens is called a diverging lens.
Reason(R) : A concave lens diverges light (bends outward) that falls on it.
a.) Both A and R are true but R is not the correct explanation of A.
b.) Both A and R are true and R is the correct explanation of A.
c.) A is true but R is false.
d.) R is true but A is false.
Ans: Both A and R are true and R is the correct explanation of A.
Fill in the blanks: (marks:1×5)
1.) ………..changes the direction of light that falls on it.
Ans: mirror.
2.) The most common example of a curved mirror is…………….
Ans: Spherical mirror.
3.) Magnifying glass is a type of…………..
Ans: convex lens.
4.) Light travels along…………….
Ans: straight lines.
5.) The white light or sunlight consists of………..colours.
Ans: seven.
Answer the following questions: (marks:1×2)
1.) What do you mean by real image?
Ans: An image which can be obtained on a screen is called a real image.
2.) What do you mean by virtual image?
Ans: An image which cannot be obtained on a screen is called a virtual image.
Answer the following questions: (marks:2× 5)
1.) What is called the reflection of light?
Ans: One way to change the direction of light is to let it fall on a shiny surface.) Mirror changes the direction of light that falls on it.) This change of direction by a mirror is called reflection of light. Any polished or a shiny surface can act as a mirror.) The surface of water can also act like a mirror and change the path of light.
2.) Write down the difference between a concave and convex mirror?
Ans:
3.) Why the convex lens is called a magnifying glass?
Ans: A convex lens can form real and inverted image. When the object is placed very close to the lens, the image formed is virtual, erect and magnified. When used to see objects magnified, the convex lens is called a magnifying glass.
4.) What is Newton’s disc?
Ans: Take a disc and divides into seven segmens. Paint the seven rainbow colours on these segments. Make a small hole at the centre of the disc. Fix the disc loosely on the tip of a refill of a ball pen. Ensure that the disc rotates freely. Rotate the disc in the daylight. When the disc is rotated fast, the colours get mixed together and the disc appears to be whitish. Such a disc is popularly known as Newton’s disc.
5.) What are the colours of a rainbow?
Ans: The rainbow is seen as a large arc in the sky with many colours. When observed carefully, there are seven colours in a rainbow, though it may not be easy to distinguish all of them. These are — red, orange, yellow, green, blue, indigo and violet.
Answer the following questions: (marks: 3×2)
1.) What is a concave mirror? What are the uses of it? (1+2)
Ans: If the reflecting surface of a spherical mirror is concave, it is called a concave mirror.
Concave mirrors are used for many purposes. Such as,
- Doctors using concave mirrors for examining eyes, ears, nose and throat.
- Concave mirrors are also used by dentists to see an enlarged image of the teeth
- The reflectors used in torches, headlights of cars and scooters are concave in shape.
2.) What is convex mirror? What are the uses of convex mirror? (1+2)
Ans: If the reflecting surface is convex, then it is a convex mirror.
Convex mirror are used for many purposes. Such as,
- Convex mirrors can form images of objects spread over a large area. So, these help the drivers to see the traffic behind them.
- It is used to produce magnifying glasses.