IIT-JEE-Physics-Screening–2000

6. Imagine an atom made up of proton and a hypothetical particle of double the mass of the electron but having the same charge as the electron. Apply the Bohr atom model and consider all possible transitions of this hypothetical particle to the first excited level. The longest wavelength photon that will be emitted has wavelength λ (given in terms of the Rydberg constant R for the hydrogen atom) equal to 
(A) 9/5R 
(B) 36/5R 
(C) 18/5R 
(D) 4/R 

7. A monoatomic ideal gas, initially at temperature T1, is enclosed in a cylinder fitted with a friction piston. The gas is allowed to expand adiabatically to a temperature T2by releasing the piston suddenly. If L1 and L2 are the lengths of the gas column before and after expansion respectively, then T1 /T2 is given by 
(A) (L1 ⁄ L2 ) 2/3 
(B) (L1 ⁄ L2 ) 
(C) L2 ⁄ L1 
(D) (L2 ⁄ L1 )2/3 

8. A point source of light B placed at a distance L in front of the centre of a mirror of width d, hangs vertically on a wall. A man walks in front of the mirror along a line parallel to the mirror at a distance 2L from it as shown. The greatest distance over which he can see the image of the light source in the mirror is 
                                                                

(A) d/2
(B) d
(C) 2d 
(D) 3d 

9. An infinitely long conductor PQR is bent to form a right angle as shown. A current I flows through PQR. The magnetic field due to this current at the point M is H1. Now, another infinitely long straight conductor QS is connected to Q so that the current is I/2 in QR as well as in QS, the current in PQ remaining unchanged. The magnetic field at M is now H2.The ratio of H1/H2 is given by 
                                                       

10. The plots of intensity versus wavelength for three black bodies at temperatures T1, T2 and T3 respectively are as shown. Their temperatures are such that

                                                    

(A) T1 > T2 > T3 
(B) T1 > T3 > T2 
(C) T2 > T3 > T1 
(D) T3 > T2 > T1

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