Calculate the power of lens, which has positive focal length of 20 cm

What is the focal length of a concave lens?

Concave lens always produces virtual image and convex lens always produces real image.
A. True
B. False

Focal length of the plano-convex lens is when its radius of curvature of the surface isR and n is the refractive index of the lens.

A science student is riding on a flat car roof train that is traveling at a constant speed of 10 mph on a straight horizontal track. The student throws a ball into the air along a path that he just made to make an initial angle of 60 degrees with the horizontal and to be in line with the track that the student's professor, who is standing nearby, observes the ball rising. How high does the ball rise vertically?

Arrange the following colours in the increasing order of their wavelengths. Violet, Red, Green, Blue:
A)Violet < Blue < Green < Red;
B)Violet < Blue < Red < Green;
C)Blue < Violet < Green < Red;
D)Violet < Green < Blue < Red

Can light be converted into mass?

Which one of the following statements is true ?
Both light and sound waves in air are longitudinal.
Both light and sound waves can travel in vacuum.
Both light and sound waves in air are transverse.
The sound waves in air are longitudinal while the light waves are transverse.

A heat pump is used to maintain a house at a constant temperature of 22degrees C. The house is losing heat to the outside air through the walls and windows at a rate of 40 MJ/J, while energy generated within the house from the people, lights and appliances amount to 6000kJ/h. For a COP of 2.4, find the power input to the heat pump

Is diffraction related to wavelength?

Arrange the following events in a chronological order.
Light from a source
Object reflects light
Reflected light enters our eye
Image formation
Light falls on an object

What is the magnification of a plane mirror?
A)1;
B)0;
C)2;
D)−1

What must be the index of refraction of the liquid such that the direction of the light entering the liquid is not changed?

What happens to a white light when it passes through a prism?

Find the diameter of the image of the moon formed by a spherical concave mirror of focal length 7.6 m. The diameter of the moon is 3450 km and the distance between the earth and the moon is 3.8 xx 10^5 km

What are the five characteristics of light?