Explanation
Correct answer (a)
Virtual image is formed when the rays of light after reflection or refraction appear to meet at a point.If light rays, after reflection or refraction, actually meets at a point then real image is formed and if they appears to meet virtual image is formed.
For example if a ray of light from the object, parallel to the principal axis, when passes through a concave lens seem to be coming out of its focus but do not actually meet.Hence a virtual image is formed.
The perception of a picture or a color stays in the human brain for a fraction of a second. Newton's color disk is a mechanical device that rotates an array of colors arranged as petals or gradients around an axis and when the disc rotates fast enough the perception of the color changes to white. This is because white light is nothing but the mixture of light of all wavelengths in the visible range.
Sir Isaac Newton used this device to prove the above assertion that white color is the mixture of all colors.
So Light is not colourless.
Correct answer is (b).
When the object is located at a location in front of the focal point, i.e. between F and O, then virtual image is formed by convex lens and the image is located behind the object and is enlarged; in other words, the image dimensions are greater than the object dimensions.
Object should be placed at infinity to obtain real, inverted and diminished image in case of convex lens. A real image is an image formed by actual rays of light. these images are always inverted, and they may be either larger or smaller than the object.
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