In myopia,what happens to the power of the eye lens?

What is meant by the least distance of distinct vision?

Which scientist established that white light is composed of seven constituent colors?

What is Tyndall effect?

In the dispersion of white light by a prism,which color of light undergoes the minimum deviation?

$(a)$ What is dispersion of white light? What is the cause of such dispersion? Draw a diagram to show the dispersion of white light by a glass prism.
$(b)$ $A$ glass prism is able to produce a spectrum when white light passes through it,but a glass slab does not produce any spectrum. Explain why this is so.