Q3 of 45 Page 304

i) Find the nature, position and magnification of the image formed by a convex lens of focal length 10cm, if the object is placed at a distance of a) 15cm b) 8cm

ii) Which of the above represents the use of convex lens in a) A film projector


b) The magnifying glass used by palm reader


a)

i) a)


Given,


Focal length (f) =+10 cm


Object length (u) = -15 cm


According to the lens formula,







Hence, the image formed is virtual and 30 cm behind the mirror.


Magnification of the object (m) =




So, the image is inverted and magnified.


b) Object length (u) = -8 cm


According to the lens formula,







Hence, the image is real and in front of the mirror.


Magnification of the object (m) =





So, the image is magnified and erect.


ii) In a film projector the image of the film is projected on a screen; to achieve this we have to get a real image of the film. So, this can be achieved by the second case of the above problem.



More from this chapter

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1

The refractive index of diamond is 2.42. What is the meaning of this statement inrelation to the speed of light?

 2

i) Redraw the diagram.


ii) This diagram represents _________


iii) Label the parts of the diagram.


iv) Mention the principle used in the device denoted bythis diagram.


 4

An object of 5cm tall is placed at a distance of 10cm from a concave mirror of radius of curvature 30cm

i) Find the nature, position and size of the image


ii) Draw the ray diagram to represent the above case.


 5

The optical prescription of a pair of spectacle is

Right eye: - 3.5 D Left eye: - 4.00 D


i) Name the defect of the eye


ii) Are these lenses thinner at the middle or at the edges?


iii) Which lens has a greater focal length?