Question

The chief function of rods and cones in the eyes of vertebrates;
(a) Rods are involved in coloured vision and cones in distinguishing light intensities
(b) Rods are important for vision in dim light and cones in bright light
(c) Rods are important for vision in bright light and cones in dim light
(d) Rods and cones are both important for vision in dim light

Answer 1

Hint: Rods and cones in the eyes of vertebrates are specialized cells that help to see. Rod cells are found in the outer edges of the retina of the eye while cones are located near the centre of the retina.

Complete answer:
Rods are strongly photosensitive cells. They detect dim light. Cones are weakly photosensitive cells. They react to bright light,
There are two types of photoreceptor cells present in the retina: rods and cones. Both are named for their general appearance. Usually, there are approximately 92 million rod cells present in the human retina. They detect dim light and are used mainly for peripheral and nighttime vision. Rods have a limited role in colour vision. Cones are absent in the optic disc, making it the blind spot. There are approximately six to seven million cones within a human eye and are mostly present near the macula. They react to bright light. The main role of cones is during the daytime for colour vision. Light is detected in rods and cones and visual information is processed in the retina Then the impulse is sent to the brain and after entering the brain the image is perceived.
So, the correct answer is “Rods are important for vision in dim light and cones in bright light”.

Note: In humans, cones far outnumber rods in the fovea i.e. the region in the centre back of the eye that is responsible for acute (central) vision. Due to this, humans have a poor night time vision.