physics MCQ help!!!!!!!please!!!!!!!

[liuweijian94]

Hey guys!!!!can any one please help me the question NOV2008 question 27 and 28~~~thank you

 

[girlscampisra]

27:
15*10^3 x 2 = 0.03 m this is the LAMBDA
v=f/lambda
3*10^8/0.03 = 1x10^10

 

[girlscampisra]

frequency is inversely propotional to LAMBDA and lambda is directly propotional to 'x' that is fringe spacing.. keep this relationship into mind and see. ans is D!

 

[bro2bro]

need hep wid 2009 nov q 23 and 29

 

[arlery]

which variant?