At what rate the images pass one after the other on a cinema screen?

Tickets are numbered from 1 to 10. two tickets are drawn one after the other at random. Find the probability that the number on one of the tickets is a multiple of 5 and on the other a multiple of 4.

An urn contains 10 black and 5 white balls. Two balls are drawn from the urn one after the other without replacement. What is the probability that both drawn balls are black?

can we obtain the image of an objetfomed by a convex mirror on the screen?

Two cards are drawn from a well shuffled pack of 52 cards one after the other without replacement. Find the probability that one of these is a queen and the other is a king of opposite colour.

Which of the two figures are the images of each other ( mirror line is the dotted line )

Two cards are drawn from a well shuffled of 52 cards. One after another without replacement. Find the probability that one of these is a red card and the other a black card.

Two nearby narrow slits are illuminated by a single monochromatic source. Name the pattern obtained on the screen. One of the slits is now covered. What is the name of the pattern now obtained on the screen? Write two differences between the pattens obtained in the two cases.

The image of an object formed by a lens on the screen is not in sharp focus.Suggest a method to get a clear focussing of the image on the screen without distrubing the position of the object,the lens or the screen.

A screen is placed 90cm from an object. The image of the object on the screen is formed by a convex lens at two different locations separated by 20cm. Determine the focal length of the lens.