The spectrum obtained from the chromosphere of the sun at the time of total solar eclipse is

• line emission spectrum

• band emission spectrum

• continuous emission spectrum

• line absorption spectrum

The nuclear reactor at Kaiga is a

• research reactor 

• fusion reactor

• breeder reactor 

• power reactor

A thread is tied slightly loose to a wire frame as in figure and the frame is dipped into a soap solution and taken out. The frame is completely covered with the film. When the portion A is punctured with a pin, the thread

• becomes concave towards A

• becomes convex towards A

• either (a) or (b) depending on the size of A with respect to B

• remains in the initial position

A beam of light of wavelength 600 nm from a source falls on a single slit 1 mm wide and the resulting diffraction pattern is observed on a screen 2 m away. The distance between the first dark fringes on either side of thecentral bright fringe is

• 2.4 cm

• 2.4 mm

• 1.2 mm

• 1.2 cm

The emitter-base junction of a transistor is ............ biased while the collector-base junction is ......... biased.

• forward, forward

• forward, reverse

• reverse, forward

• reverse, reverse

In a forward biased p-n junction diode, the potential barrier in the depletion region is of the form

A thin plano-convex lens acts like a concave mirror of focal length 0.2 m when silvered from its plane surface. The refractive index of the material of the lens is 1.5. The radius of curvature of the convex surface of the lens will be

• 0.1 m

• 0.75 m

• 0.4 m

• 0.2 m

In a Young's double slit experiment, the separation between the two slits is 0.9 mm and the fringes are observed one metre away. If it produces the second dark fringe at a distance of 1 mm from the central fringe, the wavelength of the monochromatic source of light used is

• 450 nm

• 400 nm

• 500 nm

• 600 nm

When light is incident on a diffraction grating, the zero order principal maximum will be

• spectrum of the colours

• white

• one of the component colours

• absent

50.

H-polaroid is prepared by

• orienting herapathite crystal in the same direction in nitrocellulose

• using thin tourmaline crystals

• stretching polyvinyl alcohol and then heated with dehydrating agent

• stretching polyvinyl alcohol and then impregnating with iodine