When the object and the screen are 90 cm apart, it is observed that a clear image is formed on the screen when a convex lens is placed at two positions separated by 30 cm between the object and the screen. The focal length of the lens is:
A metre scale is balanced on a knife edge at its centre. When two coins, each of mass 9 g, are kept one above the other at the 10 cm mark, the scale is found to be balanced at 35 cm. The mass of the metre scale is:
Two logic gates are connected as shown in the figure. If the inputs are \( A = 1 \) and \( B = 0 \), then the values of \( y_1 \) and \( y_2 \) respectively are: