Question

A digital video disc (DVD) records information in a spiral track approximately 1$\mu \mathrm{m}$ wide. The track consists of a series of pits in the information layer (Fig. P35. 47 $\mathrm{a}$ ) that scatter light from a laser beam sharply focused on them. The laser shines in from below through transparent plastic of thickness $t=1.20 \mathrm{mm}$ and index of refraction 1.55 (Fig.P35.47b). Assume the width of the laser beam at the information layer must be $a=1.00 \mu \mathrm{m}$ to read from only one track and not from its neighbors. Assume the width of the beam as it enters the transparent plastic is $w=0.700 \mathrm{mm}$ . A lens makes the beam converge into a cone with an apex angle 2$\theta_{1}$ before it enters the DVD. Find the incidence angle $\theta_{1}$ of the light at the edge of the conical beam. This design is relatively immune to small dust particles degrading the video quality.

          A digital video disc (DVD) records information in a spiral track approximately 1$\mu \mathrm{m}$ wide. The track consists of a series of pits in the information layer (Fig. P35. 47 $\mathrm{a}$ ) that scatter light from a laser beam sharply focused on them. The laser shines in from below through transparent plastic of thickness $t=1.20 \mathrm{mm}$ and index of refraction 1.55 (Fig.P35.47b). Assume the width of the laser beam at the information layer must be $a=1.00 \mu \mathrm{m}$ to read from only one track and not from its neighbors. Assume the width of the beam as it enters the transparent plastic is $w=0.700 \mathrm{mm}$ . A lens makes the beam converge into a cone with an apex angle 2$\theta_{1}$ before it enters the DVD. Find the incidence angle $\theta_{1}$ of the light at the edge of the conical beam. This design is relatively immune to small dust particles degrading the video quality.

Added by Matthew G.

Question

Please give Ace some feedback