Question

The blue laser in a blue ray DVD player is 405nm laser in vacuum. The aser strikes a quartz crystal with index of refraction 1.46 at normal incidence. The power of the laser is 0.25W and I'm guessing the beam is circular with radius 0.1mm. What is the intensity of the light transmitted into the crystal? Select One of the Following: (a) 7.7 x 10 (b) 1.5 x 106 W (c) 6.5 x 10% W (d) 2.85 (e) Toby.

Answer 1

This question has mistakes.the correct question is

The blue laser in a blue ray DVD player is 405nm laser in vacuum. The aser strikes a quartz crystal with index of refraction 1.46 at normal incidence. The power of the laser is 0.25W and I'm guessing the beam is circular with radius 0.1mm. What is the intensity of the light transmitted into the crystal? Select One of the Following:

(a) 7.7 x 10⁶ W/m²

(b) 1.5 x 10⁶ W/m²

(c) 6.5 x 10⁶ W/m²

(d) 2.85 W/m²

(e) Toby.

Answer:

(a) 7.7 x 10⁶ W/m² Correct

Explanation:

The Intensity of laser is given as

$I_{o}=P/A\\I_{o}=P/\pi r^{2}\\ I_{o}=\frac{0.25}{\pi (0.0001)^{2} }\\ I_{o}=7.96*10^{6} \frac{W}{m^{2} }$

The incident index of refraction and transmitted is

$n_{i}=1\\ and \\n_{t}=1.46\\I_{t}=I_{o}-I_{r}\\ I_{t}=I_{o}-(\frac{n_{i}-n_{t}}{n_{i}+n_{t}})^{2}I_{o} \\ I_{t}=(1-(\frac{1-1.46}{1+1.46} ))*7.96*10^{6} \\I_{t}=7.7*10^{6}\frac{W}{m^{2} }$