Question of Exercise 2

# Question An object AB is placed in front of a convex lens at its principle focus as shown in the figure. Which of the ray diagram below correctly depicts the refraction through the lens L.

Option 1 a convex lens

Option 2 a convex lens

Option 3 a convex lens

Option 4 a convex lens

Gobar gas is a

A: solid fuel

B: liquid fuel

C: primary fuel

D: secondary fuel

Solution:

Explanation:

• The gobar gas is a fuel classified as natural resources. Biogas is another name for gobar gas. Gobar gas is a type of gas fuel derived from cow dung (mostly from cow dung).
•  Cow dung is allowed to dry fully once all of the liquid has been removed. Dry cow dung is burnt, releasing a gas known as gobar gas,

which is mostly methane and carbon dioxide. It is composed of 55-70 percent methane, which is combustible.

We may conclude from the foregoing that gobar gas is neither a solid nor a liquid fuel. It is a kind of gas fuel.

Primary fuel is fuel that comes straight from nature. It has not been altered. For example, wood, coal, gobar gas, crude oil, and so on.

Secondary fuel is made from main fuel, which has been changed or blended with other artificial chemicals. Examples include charcoal, coke, gasoline, and hydrogen fuel.

Gobar gas is a main fuel since it is obtained directly from nature.

Hence, the correct option is (C)i.e primary fuel.

What is principal focus for concave lens

A: It is a point on the principal axis of a concave lens from which a parallel beam of light rays, travelling parallel to the principal axis, appears to come after passing through the lens.

B: It is a point on the principal axis of a concave lens from which a perpendicular beam of light rays, travelling perpendicular to the principal axis, appears to come after passing through the lens.

C: It is a point on the principal axis of a convex lens at which a parallel beam of light rays, travelling parallel to principal axis, meet after passing through the lens.

D: None

Solution:

Correct option is: (A)

Explanation:

Principal focus is a point on the principal axis of a concave lens from which a parallel beam of light rays, travelling parallel to the principal axis, appears to come after passing through the lens.

It is a point on the principal axis of a concave lens from which a parallel beam of light rays, travelling parallel to the principal axis, appears to come after passing through the lens.

Why is convex lens called converging lens

Solution:

Explanation:

When the parallel rays of light re fall on convex lens then the rays will converge and after that it meet at a point on the other side of lens.That’s why the convex lns is called converging lens.

When the parallel rays of light  fall on convex lens then the rays will converge and after that it meet at a point on the other side of lens.That’s why the convex lns is called converging lens.

What is meant by heating effect of electric current

Solution:

Explanation:

The electric current flowing in a wire produces heat that is why after some time an electric circuit becomes hot.This happens because of the resistance of the wire.

The higher the resistance of the wire, the higher will be the loss of the current in the form of heat in the circuit. Hence, this is the heating effect of electric current.

Hence, the heat produced in circuit due to electric current is the heating effect of electric current

What happens when dilute hydrochloric acid is added to iron filings? Tick the correct answer

A. Hydrogen gas and iron chloride are produced

B. Chlorine gas and iron hydroxide are produced

C. No reaction takes place

D. Iron salt and water are produced

Solution:

Ans. A

Solution.When dilute hydrochloric acid is added to iron fillings, hydrogen gas and iron chloride are produced.