Physics Test 29...

What is the De-Broglie wavelength of an electron orbiting in the n = 2 state of a hydrogen atom?

(Given: Bohr radius = 0.052 nm)

The headlight of a train of length 200 m is switched on when it starts from rest with an acceleration of 0.5 ms^–2. After 20 s, its tail-light is switched on. An observer in a frame moving with a constant velocity parallel to the railway track observes that the two events occur at the same place. The velocity of this frame is

The density inside a solid sphere of radius a is given by ρ = ρ₀ (a/r), where ρ₀ is the density at the surface and r denotes the distance from the centre. The gravitational field due to this sphere at a distance 3a from its centre is

A tuning fork with a frequency of 800 Hz produces resonance in a resonance column tube with the upper end open and the lower end closed by the water surface. Successive resonances are observed at lengths 9.75 cm, 31.25 cm, and 52.75 cm. The speed of sound in air is,

Two metal spheres, one of radius R and the other of radius 2R respectively have the same surface charge density σ. They are brought in contact and separated. What will be the new surface charge densities on them?

The output (Y) of the given logic implementation is similar to the output of an/a _______ gate.

From a solid sphere of mass M and radius R a cube of maximum possible volume is cut. Moment of inertia of cube about an axis passing through its center and perpendicular to one of its faces is :

In order to determine the Young's Modulus of a wire of radius 0.2 cm (measured using a scale of least count = 0.001 cm) and length 1 m (measured using a scale of least count = 1 mm), a weight of mass 1 kg (measured using a scale of least count = 1 g) was hanged to get the elongation of 0.5 cm (measured using a scale of least count 0.001 cm). What will be the fractional error in the value of Young's Modulus determined by this experiment? 

In a u-tube as shown in the fig. water and oil are in the left side and right side of the tube respectively. The heights from the bottom for water and oil columns are 15 cm and 20 cm respectively. The density of the oil is [take ρ_water = 1000 kg/m³]

A deep rectangular pond of surface area A, containing water (density = ρ, specific heat capacity = s), is located in a region where the outside air temperature is at a steady value of −26°C. The thickness of the frozen ice layer in this pond, at a certain instant is x. Taking the thermal conductivity of ice as K, and its specific latent heat of fusion as L, the rate of increase of the thickness of ice layer, at this instant, would be given by