Photobiology Help

1. Why are π to π * transitions on conjugated double bonds such good absorbers of

visible light?

2. Intensity of the HeNe laser (λ=632nm) was measured at 2 distances: 1 m and 200 m

from the laser. The meter reading was 10W and 1 W correspondingly. How many

photons/sec will enter your eye if you look into the laser from 1 m? From 200 m?

Assume that radius of the pupil was 2.5 mm, radius of the detector was 3.5 mm. At a

distance of 1 m the laser beam radius was 1 mm.

3. Chl has an absorbance peak at 435nm (Soret band) and a peak at 665nm

(Qytransition). Calculate the energy gap (in Joules) between the ground and excited

states of these two transitions.

Any help in the right direction would be great thanks!