Education

CBSE-Light Adjusting eye itself to deal with light of varying intensity The amount of light entering the eye is controlled by the pupil. If the intensity of the outside light is low, then the pupil expands to allow more light to enter the eye. If the outside intensity is high, then the pupil contracts so that less light enters the eye.

CBSE notes-Light Relation between Speed of light in a medium and refractive index.  Speed of the light is inversely proportional to the refractive index of the medium.

CBSE notes-Light Star light flux Star light flux is the luminous energy emitted per second by the star.

CBSE notes-Light A beam of red light is allowed to fall in turn on (a) a black cloth (b) red cloth (c) white cloth (d) blue cloth. Describe and explain the appearance in each case. (a) When red light falls on a black cloth it still appears black, because it does not reflect the red colour instead, it absorbs the light falling on it. (b) When red light falls on a red cloth it still appears red, because it reflects only that colour. (c) When red light falls on a white cloth it changes to a red coloured cloth, because the white cloth reflects the red colour of the light. (d) When red light falls on a blue cloth it changes to black coloured cloth, because there is no blue colour in the red light which can be reflected

 CBSE notes-Light What does the positive sign associated with the virtual image and the negative sign associated with the real image denote? The positive sign associated with the virtual image indicates the presence of an erect image (above the principal axis of the lens) and the negative sign associated with the real image indicates the presence of an inverted image (below the principal axis of the lens).

CBSE notes-Light Define the principal focus of a concave mirror. Light rays that are parallel to the principal axis of a concave mirror converge at a specific point on its principal axis after reflecting from the mirror. This point is known as the principal focus of the concave mirror.