Question

The figure shows two air filled bulbs $X$ and $Y$ connected by U-tube partially filled with alcohol. $X$ is painted black while $Y$ is painted white. An electric bulb $B$ is placed midway between $X$ and $Y$. When $B$ is lighted the level of alcohol in

• A. $X$ falls and in $Y$ rises
• B. $Y$ falls and in $X$ rises
• C. both $X$ and $Y$ falls
• D. both $X$ and $Y$ rises

Answer 1

The correct option is A $X$ falls and in $Y$ rises

$X$ is painted black so it absorbs more energy than $Y$ (painted white) so it gets higher temperature.
since, $P\propto T$
pressure at $X$ increases.
so temperature at $X$ falls and in $Y$ rises