The part of the human eye on which the image is formed is
- A.pupil
- B.cornea
- C.retina
- D.iris
Correct answer
Explanation
The correct answer is C, retina. The eye lens focuses light on the retina, the light-sensitive layer at the back of the eye, where a real and inverted image is formed.
The retina contains two kinds of light-sensitive cells: rods, which work in dim light and sense brightness, and cones, which work in bright light and sense colour. These cells turn light into electrical signals that travel through the optic nerve to the brain, which reads the inverted image the right way up. The point of sharpest vision, the fovea in the yellow spot, is packed with cones, while the blind spot, where the optic nerve leaves the eye, has no light-sensitive cells. The ciliary muscles change the lens’s shape so that near and far objects stay focused on the retina.
A is wrong because the pupil is only the opening through which light enters the eye. B is wrong because the cornea is the clear front surface where most of the bending of light takes place, but no image forms on it. D is wrong because the iris is the coloured muscle that controls the size of the pupil.
Exam tip: cornea bends light, iris controls pupil, lens focuses, retina forms the image, optic nerve carries it to the brain.
Practice Questions
View allOsmosis is the process of movement of water molecules from its
- A.higher concentration to its lower concentration through a cell wall.
- B.lower concentration to its higher concentration through a fully permeable membrane.
- C.higher concentration to its lower concentration through a fully permeable membrane.
- D.higher concentration to its lower concentration through a semi-permeable membrane.
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Osmosis is the passage of water from where water is more concentrated (a dilute solution) to where it is less concentrated, across a membrane that lets water through but holds back solutes.
Read the full explanation →Liquids and gases never show
- A.diamagnetic property
- B.paramagnetic property
- C.ferromagnetic property
- D.electromagnetic property
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Ferromagnetism needs the atomic magnets of a substance to line up together in fixed regions called domains, and this happens only in the ordered structure of a solid.
Read the full explanation →The chemical properties of an element depend upon
- A.the number of isotopes of the element
- B.the mass number of the element
- C.the total number of neutrons in the element
- D.the number of electrons in the outermost shell of the element
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Chemical reactions involve only the outer, or valence, electrons, so these decide how an element behaves. Atoms combine by losing, gaining or sharing their valence electrons to reach a stable arrangement, usually eight electrons in the outer shell.
Read the full explanation →Which one of the following is not found in animal cells ?
- A.Free ribosomes
- B.Mitochondria
- C.Nucleolus
- D.Cell wall
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Animal cells are bounded only by a flexible plasma membrane and have no rigid cell wall outside it. A cell wall is found in plants, where it is made mainly of cellulose, in fungi, where it is made of chitin, and in bacteria, where it is made of peptidoglycan.
Read the full explanation →A student was doing an experiment on increasing the cell division among plants. She asked her supervisor to suggest the specific plant hormone for the same. Had you been her supervisor, which plant hormone would you suggest?
- A.Abscisic acid
- B.Gibberellins
- C.Cytokinin
- D.Auxin
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Cytokinins are the plant hormones whose main job is to promote cell division, or cytokinesis, which gives them their name.
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