Question

Image formed at retina is _________ and image interpreted by brain is ________
A. erect, erect
B. erect,inverted
C. inverted, erect
D. inverted, inverted

Answer 1

Hint: The human eye is a biconvex lens. Human beings see erect images of everything around them.

Complete step by step solution:
The human eye is a biconvex lens held in place by the ciliary muscles. The ciliary muscles adjust the shape of the eye lens accordingly such that a clear image is formed on the retina. This is known as accommodation. As it is a convex lens, a real and inverted image is formed on the retina. The back of the retina has nerve endings which send nerve signals to the occipital lobe of the brain via the optic nerve. The brain processes these signals and inverts the image so that it is consistent with the surrounding. The brain also combines signals from both the eyes to give the perception of depth.

The correct answer is option (C).

Additional information: Retina has two types of photoreceptor cells: rods and cones. Rods are active in dim light conditions and give black and white vision. Cones are active in bright light conditions and are responsible for the perception of colour and visual acuity. The lack of various types of cone cells lead to colour blindness in which an individual is unable to distinguish between colours. Every human has a blind spot in the retina which doesn’t have any photoreceptor cells as the optic nerve connects to the brain here. Retina is actually a part of the Central Nervous system and is an extension of the brain.

The refractive index of human eye lenses varies between 1.406 to 1.386 approximately. The human eye can distinguish 10 million colours and remains the same size throughout life.

Note: A convex lens produces virtual image if the object distance is less than its focal length. The near point of a normal human eye is around 25 cm. It cannot focus objects closer than that.