Science
(a) Under what conditions can a convex lens form a virtual image?
(b) Why does a piece of paper catch fire if we allow sunlight to pass through a convex lens onto the paper?
Answer
(a) A convex lens can form a virtual image when the object is placed between the lens and its focal point (F). In this case, the refracted rays diverge but their backward extensions appear to meet on the same side as the object, forming a virtual, erect, and magnified image.
(b) A piece of paper catches fire when sunlight is passed through a convex lens because the lens converges the parallel rays of sunlight to a single point called the focus. This concentration of light increases the energy density and temperature at that point. When the temperature rises above the ignition point of paper, it catches fire.
Related Questions
The below image shows the formation of an image with an optical instrument.
(a) Identify the optical instrument (shown schematically as a rectangle) in the image.
(b) What type of image is formed in this case?
(c) Based on the measurements given in the image, calculate the focal length of the instrument.
Find out the following in the electric circuit given in the figure-
(a) Effective resistance of two 8 ohm resistors in the combination.
(b) Current flowing through the 4-ohm resistor
Study the circuit and find out-
(a) Current in 12 ohm resistor
(b) Difference in the readings of ammeter A1 and A2 if any