I guess that you know about the Arrhenius equation which I just came to know using google... which is:
But apart from the first part in part (b), I don't know how to tackle the problem.
For (b) use
Lambda is what you are looking for.
a) The activation energy needed to convert cis-retinal to trans-retinal is 4 × 10–19 J. What is the reaction rate for one molecule at body temperature (310 K)? In the absence of light, how long would you have to wait for a reaction to take place?
b) What wavelength of light is required to convert cis-retinal to trans-retinal? If the molecule were exposed to a blackbody at 310 K, should we expect a lot of photons with this wavelength?
Any idea how to start these?