Question

Application-based Questions
1. Make your own telephone. Take two plastic mugs and a
20 metre long, strong thread. At the bottom of each mug,
make two tiny holes. Pass the thread through one hole and
secure it firmly with a knot. Similarly pass the other end of
the thread through the hole in the second mug and fasten
firmly. Hold one mug and give the other to your friend.
Ask him to move as far away from you as the thread will
allow. The thread should be stretched tight between the
two of you. Speak into the mug and let your friend year you
at the other end. At the end of the conversation you can
call 'over and out'.
Sound vibrations travel along the length of the wire or thread and reach your friend.
A loose wire is not as effective in carrying sound as a taut wire.​

please give me fast it is urgent!!

Answer 1

Radius of curvature = 60 cm ; hence focal length f = 30 cm

We have mirror equation : begin mathsize 12px style 1 over v plus 1 over u equals 1 over f space space semicolon space space space h e n c e space 1 over v plus 1 over 10 equals negative 1 over 30 end style

where v is image to mirror distance, u is object to mirror distance. we get v = -7.5 cm from above equation.

Hence image is formed at a distance 7.5 cm behhind the convex mirror