An object of size 70 mm is place at 27 cm in front of a concave mirror of focal length 18 cm . At what distance from the mirror should a screen be placed so that a sharp focussed image can be obtained? Find the size and nature of the image.

Height of the object h 1 = 70 mm = 7 cm Object distance u = - 27 cm The focal length of a concave lens f = - 18 cm Let the image distance be found be v . According to the mirror formula, 1 f = 1 v + 1 u ∴ 1 v = 1 f - 1 u ∴ 1 v = 1 - 18 - 1 - 27 ∴ 1 v = 9 - 18 × 27 v = - 54 cm The screen should be placed 54 cm to the left of the pole to get a sharp image. Let the height of the image be found be h 2 . Magnification M is given by, M = - v u = h 2 h 1 ∴ - - 54 - 27 = h 2 7 ∴ h 2 = - 14 cm The height of the image is - 14 cm . As the image height and image distance are negative, The image is real, inverted, and enlarged.

Light enters from air to glass having refractive index 1.50 . What is the speed of light in the glass? The speed of light in a vacuum is 3 × 10 8 m s .

Given: Refractive index, n = 1.5 Refractive index, n = speed of light in vacuum speed of light in a medium ⇒ 1 .50 = 3 × 10 8 speed of light in the glass ⇒ Speed of light in glass = 2 × 10 8 m s

Name the process by which an amoeba reproduces. Draw the various stages of its reproduction in a proper sequence.

Amoeba undergoes an asexual type of reproduction where new gametes are formed without fertilization or fusion of gametes. It reproduces by the process known as binary fission. In this process, an organism divides into two, each part carrying one copy of genetic material. After replicating its genetic material through mitotic division, the cell divides into two equal-sized daughter cells.