# Explain with the help of diagrams

Explain with the help of diagrams, the effect of the following changes on the demand for a commodity:
(i) A fall in the price of substitute goods
(ii) A fall in the income of its buyer

(i)Demand for a commodity will decrease when there is a fall in the price of substitute goods, implying that demand curve would shift backward. Less will be purchased at the same price. Demand for commodity falls from OQ to O\${{Q}{1}}. So, fall in the price of tea will cause demand for coffee to fall. The given figure illustrates this situation: <img src="/uploads/db3785/original/2X/9/93d5e168d493e5a50c05fb752add97f069f5a597.png" width="295" height="231"> (ii) Demand for a commodity will decrease when there is a fall in the income of the consumer (assuming that the commodity demanded is a normal good). This would imply a backward shift in demand curve. Less will be purchased at the same price. Demand for commodity falls from OQ to O{{Q}{2}}\$. So, decrease in consumerâ€™s income will cause his demand for pure ghee to fall.
The given figure illustrates this situation: