Which one of the following statements is not correct ?
- A.Human eye is a refracting system containing a diverging lens.
- B.The retina of the human eye contains millions of light sensitive cells, called rods and cones, which convert the light into electrical messages.
- C.Every image that is focused on the retina is upside down.
- D.We need both eyes to judge the relative positions of objects accurately.
Correct answer
Explanation
The correct answer is A. The lens of the human eye is a converging (convex) lens, not a diverging one, so statement A is not correct.
Light entering the eye is bent first by the cornea and then by the crystalline lens, a convex lens whose focal length is changed by the ciliary muscles. Together they focus a real, inverted and diminished image on the retina. The retina's rods respond to dim light and cones to bright light and colour, and the optic nerve carries their signals to the brain, which reads the image the right way up. Two eyes give slightly different views, and the brain combines them to judge depth and distance.
B is wrong as a choice because it is correct: the retina has millions of rods and cones that turn light into nerve signals. C is wrong because it is correct: a convex lens forms an inverted real image on the retina. D is wrong because it is correct: judging relative position and depth needs both eyes, called binocular vision.
Exam tip: Eye lens is convex; image on the retina is real and inverted; rods for dim light, cones for colour.
Practice Questions
View allThe valency of phosphorus is
- A.2, 3
- B.3, 4
- C.4, 5
- D.3, 5
Show answer
Phosphorus has five electrons in its outer shell and shows two common valencies, 3 and 5. Phosphorus, atomic number 15, has the electronic configuration 2, 8, 5.
Read the full explanation →Which one of the following statements is NOT correct ?
- A.Single celled eukaryotes belong to Kingdom Protista
- B.Yeast, a fungus is multicellular
- C.The fungi constitute a unique kingdom of heterotrophs
- D.Ascomycetes, a saprophytic fungi is multicellular or rarely unicellular
Show answer
This statement is false, because yeast is one of the few fungi that are unicellular. In Whittaker's five-kingdom system, fungi form a separate kingdom.
Read the full explanation →Desalination of seawater is done by using reverse osmosis. The pressure applied to the solution is
- A.larger than osmotic pressure
- B.smaller than osmotic pressure
- C.equal to osmotic pressure
- D.equal to atmospheric pressure
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Read the full explanation →Which one of the following does not form oxide on reaction with oxygen?
- A.Magnesium
- B.Lead
- C.Tin
- D.Silver
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Silver sits near the bottom of the reactivity series and does not combine with oxygen even when heated in air.
Read the full explanation →The foul smell of urine of a healthy man having healthy food, when spilled on floor, is mainly due to the bacterial decomposition of
- A.urea into sulphur dioxide
- B.sugar into carbon dioxide
- C.lipids into methane
- D.urea into ammonia
Show answer
Bacteria on the floor break down the urea in urine and release ammonia, which has a sharp, pungent smell. Urea, CO(NH2)2, is the main nitrogenous waste of humans.
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