The Rhodopsin molecules in the retain contain a derivative of vitamin A called cis-retinal (Figure 6). On exposure to light, cis-retinal becomes an isomer called trans-retinal (Textbook Question).
The answer is bond 11 (shown in red).
What I don't understand is: I thought rotation is not allowed around double bonds.
So when light hits Figure $6$, how does it cause rotation around bond $11$ to form Figure $7$?