The work function for Tungsten and Sodium are 4.2 eV and 2.3 eV, respectively. If the threshold wavelength for Sodium is 5460 \(\text{\AA}\), then that for tungsten is :

The power and aperture of lenses L1, L2 and L3 are given below in tabular format. Which pair of lenses should be chosen for constructing a microscope?

Lens	Power	Aperture
L1	3D	8 cm
L2	6D	1 cm
L3	10D	1 cm

A circular loop of 20 turns carries a current of 5.0 A. If the magnetic field at the centre of the loop is 1.57 mT, the radius of the loop would be :

Which of the followings should be doped with pure silicon to get an n-type and p-type semiconductors respectively?

The energy equivalent of 10 g of substance is:

A dentist has a small mirror of focal length \(1 . 6 ~ c m\). He observes the cavity in the tooth of a patient by holding the mirror at a distance of 8 mm . from the cavity. The magnification is:

A uniform electric field of 20 V m -1 exists in the vertically downward direction. What will be the increase in the electric potential as one goes up through a height of 60 cm?

Three mangoes and three apples are kept in a box. If two fruits are selected at random from the box, the probability that the selection will contain one mango and one apple is :

A nucleoside comprises:

The loss of strength of a signal while propagating through a medium is called-

Read the passage carefully and answer the questions based on the passage:
Species diversity on earth is not uniformly distributed. It is generally highest in the tropics and decreases towards the poles. Earth's fossil history reveals the incidences of mass extinctions in the past. Earth's rich biodiversity is vital for the very survival of mankind. It is believed that communities with high diversity tend to be less variable and more productive. The reasons of conserving biodiversity are narrowly utilitarian, broadly utilitarian and ethical. Biodiversity conservation may be in-situ as well as ex-situ.
Which of the following might not account for the greater biological diversity in the tropic region?

The power of the composite lens made of two thin lenses of focal lengths \(f_1\) and \(f_2\) placed in contact will be:

An electric source has an emf of 130 V and a terminal voltage of 110 V. If it supplies a terminal current of 20 A, its internal resistance will be