Question

What difference is seen in the intensity of the image (brightness) of the image of the flame on the screen?

Answer 1

HintUnderstand the lens formula and apply the equation for the given case study question. For the size of the image get to know about the magnification formula. Find out how magnification has an impact on the intensity of the image.

Complete answer:
For the given statement, we have identified that in order to obtain a clear image, the student needs to move the lens towards the source to focus the source on the screen. As and when he moves the lens, the image gets magnified, due to increase in intensity and bombardment of light rays. As we move towards the lens, the magnification factor m is increased. Assuming when the light is near the lens, the u distance is less and hence the image will be of negative magnification factor.
If the source is near the lens, the image is said to have high magnification with greater intensity. And when the image is moved farther from the source, the magnification increases, thus reducing the intensity of the image.
The intensity is reduced as light waves are forced to travel to longer distances to meet and form a magnified image. Thus as distance increases, the intensity of the image formed decreases.
Thus the light intensity formed on the screen decreases.

Note
Intensity of light is the measure of weight of the wavelength of light waves that is propagating from origin to a final point , in a particular direction. It is known that light travels in a straight line. The fundamental unit is Candela (cd), which is the S.I unit for light intensity.