Advertisement

An object 5 cm in length is held 25 cm away from a converging lens of focal length 10 cm. Draw the ray diagram and find the position, size and the nature of the image formed.


Converging lens means a convex lens. As the distances given in the question are large, so we choose a scale of 1: 5, i.e., 1 cm represents 5 cm. Therefore, on this scale 5 cm high object, object distance of 25 cm and focal length of 10 cm can be represented by 1 cm high, 5 cm and 2 cm lines respectively. Now, we draw the ray diagram as follows:
(i) Draw a horizontal line to represent the principal axis of the convex lens.
(ii) Centre line is shown by DE.
(iii) Mark two foci F and F' on two sides of the lens, each at a distance of 2 cm from the lens.
(iv) Draw an arrow AB of height 1 cm on the left side of lens at a distance of 5 cm from the lens.
(v) Draw a line AD parallel to principal axis and then, allow it to pass straight through the focus (F') on the right side of the lens.
(vi) Draw a line from A to C (centre of the lens), which goes straight without deviation.
(vii) Let the two lines starting from A meet at A'.
(viii) Draw AB', perpendicular to the principal axis from A'.
(ix) Now AB', represents the real, but inverted image of the object AB.
(x) Then, measure CB' and A'B'. It is found that CB' = 3.3 cm and A'B' = 0.7 cm.

Converging lens means a convex lens. As the distances given in the qu

(xi) Thus the final position, nature and size of the image A'B' are:
         (a) Position of image A'B' = 3.3 cm × 5 = 16.5 cm from the lens on opposite side.
         (b) Nature of image A’B’: Real and inverted. 
         (c) Height of image A'B': 0.7 × 5 = 3.5 cm, i.e., image is smaller than the object.



 
586 Views

Advertisement
Which of the following lenses would you prefer to use while reading small letters found in a dictionary?
  • A convex lens of focal length 50 cm
  • A concave lens of focal length 50 cm
  • A convex lens of focal length 5 cm

  • A concave lens of focal length 5 cm

We wish to obtain an erect image of an object, using a concave mirror of focal length 15 cm. What should be the range of distance of the object from the mirror? What is the nature of the image? Is the image larger or smaller than the object? Draw a ray diagram to show the image formation in this case.

Name the type of mirror used in the following situations:
(a) Headlights of a car.
(b) Side /rear-view mirror of a vehicle
(c) Solar furnace.
Support your answer with reason.

One-half of a convex lens is covered with a black paper. Will this lens produce a complete image of the object? Verify your answer experimentally. Explain your observations.





First 4 5 6 Last
Advertisement