An object is kept at a distance of 18cm,20cm,22cm and 30cm from the lens of power +5D
a] in which case would you get a magnified image
b]which of the magnified image can we get on a screen
Answers
Focal length of the lens, F = 1/ Power of the lens
⇒ F = 1/P
⇒ F = 1/5
⇒ F = 0.2 m
⇒ F = 20 cm
To get the magnified image the concave lens cannot be used as it forms the dimisnished image only.
So we can use a convex lens to do so.
Location and Characteristics of Images Formed by a Convex Lens
Object Location Image Location Nature of Image
Infinity At F2 Real Inverted
Beyond 2F1 Between F2 and 2F2 Real Inverted
At 2F1 At 2F2 Real Inverted
Between 2F1 and F1 Beyond 2F2 Real Inverted
At F1 Infinity Real Inverted
Between F1 and O On the same side as the object Virtual Erect
From the above table we can say that If the object is between the focus and center of curvature it forms Real, Inverted and Magnified image at the center of curvature of the lens on the other side of the object.
If the object is between the focus and optic center it forms Virtual, Erect, and Magnified on the same side of the object.
If the object At the focus of the lens it forms Real, Inverted and Highly Magnified at Infinity.
As the focal length of the given lens is 20 cm its radius of curvature is 40 cm. So if the object is placed at the distances 22cm, and 30cm they will be between the focus and the centre of the curvature for the lens. The respective images formed are magnified.
Answer:
Explanation:(i) P=1/f, f=100/5=20 cm An object at 20 cm, 22 cm, and 30 cm, the image can be magnified. (ii) At 22 cm and 30 cm, the image can be obtained on a screen.