Which of the following statements is not correct?
Answer: (C) Rods are very sensitive and contribute to daylight vision.. Answer: (c) — The statement that rods contribute to daylight (photopic) vision is not correct.
- A.An action potential in an axon does not move backward because the segment behind is in a refractory phase
- B.Depolarisation of hair cells of cochlea results in the opening of the mechanically gated potassium-ion channels.
- C.Rods are very sensitive and contribute to daylight vision.✓
- D.In the knee-jerk reflex, stimulus is the stretching of muscle and response is its contraction.
Correct Answer
(C) Rods are very sensitive and contribute to daylight vision.
Solution & Explanation
Answer: (c) — The statement that rods contribute to daylight (photopic) vision is not correct. Solution: Rods function in dim-light (scotopic) vision, while cones handle bright-light/colour vision, so attributing daylight vision to rods is wrong (eye photoreceptor detail is removed content, handled here in prose only). On the in-syllabus nerve-impulse side, after depolarisation K+ rapidly diffuses out and restores the resting potential, making the fibre once more responsive to further stimulation — a correct statement about the action potential and refractory recovery. NCERT Reference: Ch 18, p.233, lines 26-28 — "restores the resting potential of the membrane at the site of excitation"