1)Mention any two functions of epidermis(Biology)
2)In a voltmeter there are 20 divisions between the 0 marks and 0.5 mark.Calculate the least count of the voltmeter.(Physics)
3)Describe any five safety measures that should be taken while dealing with electric appliances connected in domestic electric circuit.(Physics)
4)With the help of ciliary muscles,the human eye can change its curvature and thus alter the focal length of its lens.State the changes that occur in the curvature and focal length of the eye lens while viewing (a)A distant object.(b)A nearby object.Explain why a normal eye is not able to see distinctly the object placed closer than 25cm,without putting any strain on the eye.(Physics)
Answers
1.*The epidermis acts as a barrier that protects the body from ultraviolet (UV) radiation, harmful chemicals, and pathogens such as bacteria, viruses, and fungi.
*it is a complex system that plays a key role in how the immune system communicates and target defense.
2.
Least Count=
Value of one main scale division/
Total number of scale divisions
=0.5/20
=0.025V
3.(i) To avoid shocks from electrical appliances use proper-earthing arrangement.
(ii) Replace old worn out and damaged wires with new set
(iii) Put the main switch off when removing any fault in electric circuits.
(iv) Wear rubber shoes and gloves while dealing with replacement of any appliance.
(v) Work with electric circuits in proper light.
(vi) Do not put your hand inside water being heated with immersion rod, when the rod is inside and on.
4.
(a) When we see distant objects, the ciliary muscles relaVexpand to decrease the curvature and thereby increase the focal length of the lens. Hence, the lens becomes thin. This enables us to see the distant object clearly. Thus, the focal length of the eye lens increases while seeing distant objects.
(b).To see the nearby objects clearly, the focal length of the lens should be shorter. For this, the ciliary muscles contract to increase the curvature and thereby decrease the focal length of the lens Hence, the lens becomes thick. This enables you to see the nearby objects clearly.
A normal eye is not able to see distinctly the objects placed closer than 25 cm, without putting any strain on the eye. This is because the ciliary muscles of eyes are unable to contract beyond a certain limit. If the objects are placed at a distance of less than 25 cm from the eye, then the objects appear blurred because light rays coming from the object meet beyond the retina.
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