4.The Dolphin emits short bursts of ultrasound. The echoes of the ultrasound help the dolphins find fish. A SONAR receives a strong echo of ultrasonic signal it sent downwards into the sea 3.6 seconds after the transmission. Calculate the depth of the sea-bed if the speed of ultrasonic waves in sea-water is 1500 m/s.

How does the image distance (di) of a convex lens compare with the image distance of a concave lens? a. the image distance of the convex lens is positive, and that of the concave lens is negative. b. both are negative for a virtual image. c. both are positive for a virtual image d. the image distance of the convex lens is negative, and that of the concave lens is positive.

J. j. thomson’s experiment disproved the theory that an atom

Which is an example of an exothermic process?