Explain the terms: principal axis, optical centre, and principal focus of a converging lens. Also, calculate the image distance and magnification for an object placed 15 cm away from a converging lens

You're on a roll — here are the solutions to question 7: 7. a) i) The principal axis is an imaginary straight line passing through the optical centre of the lens and perpendicular to its surfaces. ii) The optical centre is the central point of a lens through which light rays pass without undergoing any deviation. iii) The principal focus (or focal point) of a converging lens is the point on the principal axis where parallel rays of light, after passing through the lens, converge. b) Given: Object distance, u = 15 cm Focal length of converging lens, f = 10 cm i) Since the object is placed between f (10 cm) and 2f (20 cm) for a converging lens, the image formed is real, inverted, and magnified. ii) To calculate the image distance (v), use the lens formula: (1)/(f) = (1)/(u) + (1)/(v) Rearrange to solve for v: (1)/(v) = (1)/(f) - (1)/(u) Substitute the given values: (1)/(v) = (1)/(10 cm) - (1)/(15 cm) Find a common denominator: (1)/(v) = (3)/(30 cm) - (2)/(30 cm) (1)/(v) = (1)/(30 cm) v = 30 cm The image distance is 30 cm. iii) To calculate the magnification (M), use the formula: M = (v)/(u) Substitute the values: M = 30 cm15 cm M = 2 The magnification is 2. c) Two differences between the eye and a camera are: • The eye focuses by changing the focal length of its lens (accommodation), while a camera focuses by changing the distance between its lens and the film/sensor. • The eye uses a retina as its light-sensitive part, whereas a camera uses photographic film or a digital sensor (CCD/CMOS). d) Two applications of total internal reflection are: • Optical fibers: Used for high-speed data transmission and in medical endoscopes. • Periscopes and binoculars: Use prisms to reflect light, allowing for compact designs and brighter images. Last free one today — make it count tomorrow, or type /upgrade for unlimited.