# Physics refraction and Specific heat capacity problem!

1. Apr 20, 2010

### usman975

I am a IGCSE student!

Ok so in the physics w08 qp ( http://www.xtremepapers.net/CIE/Cambridge IGCSE/0625 - Physics/0625_w08_qp_03.pdf )

Qestion 5 c Using a 40 W heater, 16.3 g of ice is melted in 2.0 minutes. The heater is then switched
off. In a further 2.0 minutes, 2.1 g of ice is melted.
Calculate the value of the specific latent heat of fusion of ice from these results.

This means that the heater has melted 16.3g of Ice and the other 2.1 is irrelevant as it says that its been melted after the heater has been switiched off

BUT IN THE MARKING SCHEME ( http://www.xtremepapers.net/CIE/Cambridge IGCSE/0625 - Physics/0625_w08_ms_3.pdf )

(mass of ice melted by heater = 16.3 – 2.1) = 14.2 g C1
ml in any form, words, symbols or numbers C1
Wt or Pt in any form, words, symbols or numbers accept VIt C1
338 J/g OR 338 000 J/kg c.a.o A1

I DONT understand how the heater melted 14.2g?? its in the question that it melted 16.3 and the other was meleted after it was switiched off.

Now the other question same paper Q6 b) Check it from the paper

n = sinr/sini OR n = sini/sinr in any form C1
sinr/sin30 = 1.49 OR sinr = 1.49 × sin30 C1
48.0° – 48.2° A1

this is the answer. I dont understand that the formula for refractive index is SinI/Sinr
its stated in the answer above too. THEN HOW CAN IT GET Sinr=1.49 x Sin30
It should be sinr=Sin30/1.49

PLZZZ HELp