A siren emitting a sound of frequency 800 Hz moves away from an observer towards a cliff at a speed of $15 ms^{-1}.$Then, the frequency of sound that the observer hears in the echo reflected from the cliff is (Take velocity of sound in air = 330$ms^{-1}$)

A particle of mass 10 g moves along a circle of radius 6.4 cm with a constant tangential acceleration. What is the magnitude of this acceleration if the kinetic energy of the particle becomes equal to 8 × 10⁻⁴ J by the end of the second revolution after the beginning of the motion?

Consider the molecules $CH_4, NH_3$ and $H_2O.$

A system of rotating crops with legume or grass pasture to improve soil structure and fertility is called

Mitochondria and chloroplast are (a) semi-autonomous organelles (b) formed by division of pre-existing organelles and they contain DNA but lack protein synthesizing machinery. Which one of the following options is correct?

In context of amniocentesis, which of the following statement is incorrect?

In a chloroplast the highest number of protons are found in

Photosensitive compound in human eye is made up of