Light Energy Test - 1

Ray optics is valid when characteristic dimension are much larger than wavelength of light . The size of obstacle must be much larger than the wavelength of light. If wavelength is comparable to the size of object, then diffraction could happen, but it cannot be explained using ray optics, it will require wave theory of light.

According to the question the correct option will be ‘D’ because when light rays are passed through a prism, the phenomenon that happens is known as the dispersion of light. The splitting of white light into its constituent colors is known as dispersion.

According to the question the correct option will be ‘C’ because Concave mirrors are used in the headlights of a car.

When a lighted bulb is placed at the focus of a concave reflector, the reflector collects the light rays and directs them into a powerful beam (in form of parallel rays) after

reflection. Such beam can reach a large distance in dark and enable vision up to greater distances. 

According to the question the correct option will be ‘C’ because Concave mirrors are used in torches used at homes or by dentists.

In a torch, the bulb is placed at the focal point of the concave mirror so the light from the bulb is reflected as a parallel beam. This helps users to specifically see the desired object.

According to the question the correct option will be ‘A’ because Image formed by a plane mirror is erect and always of the same size as the object. The image formed by a convex mirror is upright but reduced in size whereas in a concave mirror the size of image is not fixed.

According to the question the correct option will be ‘D’ because Newton's disc has different segments painted in different colors. They are painted in the order of Violet, Indigo, Blue, Green, Yellow, Orange and Red. When the disc is rotating, all the colors appear to be white. Isaac Newton used this disc to demonstrate that white light is a combination of the seven different colors.

According to the question the correct option will be ‘B’ because the Convex mirrors are commonly used as rear-view mirrors in vehicles because they give erect, virtual and diminished images of distant objects with a wider field of view. Thus, convex mirrors enable the driver to view a much larger area than would be possible with a plane mirror.

According to the question the correct option will be ‘C’ because For a convex mirror, the radius of curvature R, is twice its focal length f.

R=2f

30=2f

f=15

Therefore, the focal length f=15 cm

According to the question the correct option will be ‘B’ because the colors in the rainbows are labeled as VIBGYOR.

VIBGYOR stand for violet, indigo, blue, green, yellow, orange and red.

According to the question the correct option will be ‘A’ because The bouncing back of light from a shiny surface without absorption of it is called as reflection. Reflection always follows certain laws called the laws of reflection. The laws are as follows:

1. Angle of incidence is equal to the angle of reflection.

2. The incident ray, normal and the reflected ray lie in the same plane.