Prabin Kalikote

a. Principal axis:
The line joining both the centers of curvature of a lens is called the principal axis.

b. Optical center:
The geometrical center of a lens is known as its optical center.

c. Center of curvature:
The center of the sphere from which the lens has been cut is called the center of curvature.

d. Focal length:
The distance between principle focus and optical center is called the focal length.

e. Far point:
The distance point from the eye seen clearly is called...

The different types of lens are:

Convex lens: A lens that is thick in the middle and thin at the edge is called a convex lens.

Concave lens: A lens that is thick at the edges but thin in the middle is called a concave lens.

A lens is a piece of transparent glass bounded by two refracting surfaces which are usually spherical.

Two uses of the lens are:

1. It is used in the human spectacle.
2. It is used in scientific projects.
   

It means one kilogram mass of B requires 470J of heat to raise its temp. by 1⁰C.

C will have the highest temperature because it has the lowest sp. heat capacity and B will have the lowest temperature because it has the highest sp. heat capacity.
From: sp. heat capacity  1/temperature.

B will make the deepest hole in the wax slab because it has more heat to release to the wax slab as it is with constant mass and temp. with the highest sp. heat capacity.

A new quilt has high air storage capacity as it is thicker than the old one, But the old quilt can't store more air as it is compressed by several uses. So, a new quilt acts as a better insulator than the old one. So, a new quilt prevents our body's heat to be released into the atmosphere in a better way than the old one. Hence, a new quilt is warmer than an old one.

In the winter season, the morning temp. on the earth's surface is very low. But the inner core of the earth is always hot. We know, well water is absorbed from deep inside the ground. At that surface, water absorbs the heat from the earth's core and remains hot. When the same water is brought to the surface, the temp. of water is higher than that of surroundings. So, well water is felt to be warmer in the morning during the winter.

We all know that water has the highest specific heat capacity. So, it absorbs more heat and also loses more heat. During the day, the heat near the sea area is absorbed by water in the sea and during the night the area near the sea absorbs heat from the sea.
So, the temp near the sea remains moderate.