A singer, holding a note of the right frequency, can shatter a glass if the glassware is of high quality. This cannot be done if the glass ware quality is low. Explain why.

Resonance is the phenomenon of setting a body into vibrations by a strong periodic force whose frequency coincides with the natural frequency of the body. Since in resonance the body absorbs maximum energy from the impressed source that results the amplitude of vibrations is very large.
Shattering a wine glass with a sound wave that matches one of the natural frequencies of the glass is but one demonstration of this effect. If the glass quality is low, the resonance frequency cannot be matched with its right natural frequency. That is why it cannot be done if the glassware quality is low