Short Answer TypeAn object of height 2.5 cm is placed at a distance of 15 cm from the optical centre ‘O’ of a convex lens of focal length 10 cm. Draw a ray diagram to find the position and size of the image formed. Mark optical centre ‘O’, principal focus F and height of the image on the diagram.
Long Answer TypeWhat is placenta? Describe its structure. State its functions in case of a pregnant human female.
Placenta is a special tissue that forms a connection between the foetus and the mother. It is a disc embedded in the uterine wall, it contains villi on the embryo’s side of the tissue while there are blood spaces on the Mother's side, which surround the villi.
Function of placenta
The placenta acts as a respiratory and excretory surface.
i. It provides a large surface area for glucose and oxygen to pass from the mother to
the embryo.
ii. It also helps to remove the waste substances generated by the foetus by transferring them into the mother’s blood.
Define evolution. How does it occur? Describe how fossils provide us evidences in support of evolution.
It is desired to obtain an erect image of an object, using concave mirror of focal length of 12 cm
(i) What should be the range of distance of an object placed in front of the mirror?
(ii) Will the image be smaller or larger than the object. Draw ray diagram to show the formation of image in this case.
(iii) Where will the image of this object be, if it is placed 24 cm in front of the mirror ? Draw ray diagram for this situation also to justify your answer.
Show the positions of pole, principal focus and the centre of curvature in the above ray diagrams.
(a) Define optical centre of a spherical lens.
(b) A divergent lens has a focal length of 20 cm. At what distance should an object of height 4 cm from the optical centre of the lens be placed so that its image is formed 10 cm away from the lens. Find the size of the image also.
(c) Draw a ray diagram to show the formation of image in above situation.What is atmospheric refraction? Use this phenomenon to explain the following natural events:
a) Twinkling of stars
b) Advanced sunrise and delayed sunset
Draw diagrams to illustrate your answer.
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