A stretched string is fixed at both ends. It is made to vibrate so that the total number of nodes formed in it is ' $x$ '. The length of the string in terms of the wavelength of waves formed in it is ( $\lambda=$ wavelength $)$

Three long, straight parallel wires carrying currents are arranged as shown. The wire C which carries a current of 5.0 A is so placed that it experiences no force. The distance of wire C from wire $D$ is

Which of the following statements about the Bohr model of the hydrogen atom is false?

Two points separated by a distance of 0.1 mm can just be seen in microscope when light of wavelength $6000 \mathop A\limits^o $ is used. If the light of wavelength $4800 \mathop A\limits^o $ is used, the limit of resolution will become