Which of the following is most reactive towards alcoholic $KOH$?

Fresnel diffraction is produced due to light rays falling on a small obstacle. The intensity of light at a point on a screen beyond an obstacle depends on

Which of the following is $NOT$ a characteristic of the phylum $Annelida$?

Which of the following oxides is different from the other three oxides?

Which of the following is not used as a biopesticide?

Light of wavelength $\lambda$ is incident on a single slit of width $a$ and the distance between the slit and the screen is $D$. In the diffraction pattern,if the slit width is equal to the width of the central maximum,then $D$ is equal to: