An object is placed at a distance of 40 cm from a  concave mirror of focal length 15 cm. If the object is displaced through a distance of 20 cm towards the mirror, the displacement of the image will be

A beam of light of \(\large \lambda \) = 600 nm from a distant source falls on a single slit 1 mm wide and the resulting diffraction pattern is observed on a screen 2m away. The distance between first dark fringes on either side of the central bright fringe is :

In the Young's double slit experiment the intensity of light at a point on the screen where the path difference is '\(\large \lambda \) is K, ('\(\large \lambda \) being the wave length of light used). The intensity at a point where the path difference is \(\large \lambda \)/4, will be :

In a double slit experiment, when light of wavelength 400 nm was used, the angular width of the first minima formed on a screen placed 1 m away, was found to be 0.2°. What will be the angular width of the first minima, if the entire experimental apparatus is immersed in water? (\(\large \mu_{water}\) = 4/3)

In Young’s double slit experiment the separation d between the slits is 2 mm, the wavelength \(\lambda\) of the light used is 5896 Å and distance D between the screen and slits is 100 cm. It is found that the angular width of the fringes is 0·20°. To increase the fringe angular width to 0·21° (with same \(\lambda\)and D) the separation between the slits needs to be changed to