How does phototropism occur in plants?

(N/A) Phototropism is the directional growth of a plant in response to light.
$1$. When plants are exposed to light coming from one side,a plant hormone called $Auxin$ is synthesized at the shoot tip.
$2$. $Auxin$ helps the cells grow longer.
$3$. When light falls on the shoot from one side,$Auxin$ diffuses towards the shady side of the shoot.
$4$. This concentration of $Auxin$ stimulates the cells on the shady side to grow longer than those on the side receiving light.
$5$. As a result,the plant appears to bend towards the source of light.