Question

1..focus of a very thin concave lens is 10 cm then its radius of curvature is
a)20 cm
b)5cm
c)10cm
d)40cm
2.80 cal of heat is required to convent 1 gr ice into water then the quantity of heat required to change 10 gr ice into water is
a)80cal
b)8cal
c)800cal
d) 8000cal
3.which pair of chemicals of the following gives common salt
a) nitrogen, chlorine
b) zinc ,hydrogen chloric acid
c)sodium sulphate, barium choloride
d) nitric acid , sodium carbonate

Answer 1

1)We know that R=2f

R= 2*10=20cm

2)L=Qm= 80*10= 800cal

3)c