The figure given below shows a radioactive nucleus A composed of 84 protons and 128 neutrons kept in a thick lead walled container. The emitted particles pass through a magnetic field in a direction perpendicular to the plane of paper inwards as shown by X. The nucleus A emits a particle which deflects to the left and is transformed into nucleus B. Nucleus B further emits a particle which deflects towards right and transforms into nucleus C.

(a) Name the radiations emitted by nucleus A and B.

(b) Name the law used to identify the radiations.

(c) What is the composition of nucleus C?

Jatin puts a pencil into a glass container having water and is surprised to see the pencil in a different state.

(a) What change is observed in the appearance of the pencil?

(b) What is the reason for this change?

(c) Classify the following as a real or virtual image:
The image of a candle flame formed on a screen by a convex lens.

The figure given below shows the experimental set up for the determination of focal length of a lens using a plane mirror.

(a) Draw two rays from the point O of the object to show the formation of image I at O itself.

(b) What is the size of the image I?

(c) A convex lens of short focal length is used in which optical instrument?

(d) The focal length of a convex lens is 25 cm. Express its power with sign.

A lens of focal length 15 cm forms an erect image three times the size of the object on a screen.

(a) What kind of lens is this?

(b) Find the position of the object from the lens.

(c) Find the position of the screen from the lens.