31.

A wire carrying current I has the shape as shown in the adjoining figure. Linear parts of the wire are very long and parallel to X  -axis while semicircular portion of radius R is lying in a Y-Z plane. The magnetic field at point  O is.

• 
• 
• 
• 

An electron moving in a circular orbit of radius r makes n rotations per second. The magnetic field produced at the centre has magnitude.

• 

• zero

• 
• 

A conducting square frame of side 'a' and a long straight wire carrying current I are located in the same plane as shown n the figure. The frame moves to the right with constant velocity 'v'. The emf induced in the frame will be proportional to

On observing light from three different stars P, Q and R, It was found that intensity of violet colour is maximum in the spectrum of P, the intensity of green colour is maximum in the spectrum of R and the intensity of red colour is maximum in the spectrum of Q. If T_P, T_Q and T_R are the respective absolute temperature of P, Q and R, then  it can conclude from the above observations that

• T_P > T_Q>T_R
  

• T_P > T_R> T_Q

• T_P > T_R < T_Q

• T_P > T_R < T_Q

A radiation of energy 'E' falls normally on a perfectly reflecting surface. The momentum transferred to the surface is 
(c = velocity of light)

In a double slit experiment, the two slits are 1 mm apart and the screen is placed in 1 m away. A monochromatic light of wavelength 500nm is used. What will be the width of each slit for obtaining ten maxima of double slit within the central maxima of double slit within the central maxima of single slit pattern?

• 0.2mm

• 0.1 mm

• 0.5 mm

• 0.5 mm

The refracting angle of a prism is A,  and the refractive index of the material of the prism is cot (A/2). The angle of minimum deviation is

• 180^o-3A

• 180^o-2A

• 90^o-A

• 90^o-A

Consider 3^rd orbit of He⁺ (Helium)_, using non-relativistic approach, the speed of electron in this orbit will be (given K= 9 x 10⁹ constant, Z=2 and h (Planck's constant = 6.6 x 10^-34 Js^-1

• 2.92 x 10⁶ m/s

• 1.46 x 10⁶ m/s

• 0.73 x 10⁶ m/s

• 0.73 x 10⁶ m/s

If radius of the  nucleus is taken to be R_Al, then the radius of  nucleus is nearly

For a parallel beam of monochromatic light of wavelength 'λ'diffraction is produced by single slit whose width 'a' is of the order of the wavelength of the light. If 'D' is the distance of the screen from the slit the width of the central maxima will be

• 2Dλ/a

• Dλ/a

• Da/λ

• Da/λ