NCERT Solutions for Class 7th Science
Chapter 15. Light
Ques: What is concave mirror?
Ans: If the reflecting surface of a spherical mirror is concave, it is called a concave mirror.
Ques: What is convex mirror?
Ans: If the reflecting surface is convex, then it is a convex mirror.
Ques: What is real image?
Ans: An image formed on a screen is called a real image.
Ques: What is virtual image?
Ans: The image formed by a plane mirror could not be obtained on a screen. Such an image is called a virtual image.
Ques: Which type of mirror can form a real image?
Ans: Concave mirror.
Ques: Which type of lens forms always a virtual image?
Ans: Concave lens.
Ques: Give one use each of a concave and a convex mirror.
Use of Concave Mirror-
(i) In Head-lights of Vehicles
Use of Comcave Mirror-
(i) It is used in vehicles as side mirror.
Ques: What is convex lens?
Ans: Those lenses which feel thicker in the middle than at the edges are convex lenses.
Ques: What is concave lens?
Ans: Those which feel thinner in the middle than at the edges are concave lenses.
Ques: Why is convex lens called converging lens?
Ans: A convex lens converges (bends inward) the light generally falling on it. Therefore, it is called a converging lens.
Ques: Why is concave lens called diverging lens?
Ans: A concave lens diverges (bends outward) the light and is called a diverging lens.
Ques: Which lens is used as magnificent lens?
Ans: convex lens.
Ques: What is white light?
Ans: The sunlight consists of seven colours. The sunlight is said to be white light.
Ques: Name all colours presence in rainbow in their real order.
Ques: Name all colours consist in white light.
Ans: red, orange, yellow, green, blue, indigo and violet.
Ques: How many colours are there in white light.
Ques: Fill in the blanks:
(i) An image that cannot be obtained on a screen is called _________.
(ii) Image formed by a convex __________ is always virtual and smaller in size.
(iii) An image formed by a __________ mirror is always of the same size as that of the object.
(iv) An image which can be obtained on a screen is called a _________ image.
(v) An image formed by a concave ___________ cannot be obtained on a screen.
(i) Vertual image