Light – Reflection and Refraction — Science STD 10 — Question

A battery of 9 V is connected in series with resistors of 0.2 Ω, 0.3 Ω, 0.4 Ω , 0.5 Ω and 12 Ω, respectively. How much current would flow through the 12 Ω resistor?

Write down the magnification formula for a lens in terms of object distance and image distance. How does this magnification formula for a lens differ from the corresponding formula for a mirror?

Explain why, when it is getting dark at night, it is impossible to make out the colour of cars on the road.

A substance X is added to LPG cylinders while filling so as to make the detection of leakage of LPG from the cylinder easy.

1. Name the substance X.
2. How does substance X make the detection of leakage of LPG easy?

Why does the sun appear reddish early in the morning? Will this phenomenon be observed by an astronaut on the Moon? Give reason to justify your answer.

With the help of a ray diagram, determine the position, nature and size of the image formed of an object placed at the centre of curvature of a concave mirror.

The absolute refractive indices of glass and water are 4/3 and 3/2 respectively. If the speed of light in glass is 2 x10⁸ m/s, calculate the speed of light in (i) vacuum, (ii) water.

In an experiment to study the relation between the potential difference across a resistor and the current through it, a student recorded the following observations:
  

Potential V (volts)	1.0	2.2	3.0	4.0	6.4
Current I (ampere)	0.1	0.2	0.6	0.4	0.6

On examining the above observations the teacher asked the student to reject one set of readings as the values were out of agreement with the rest. Which one of the above sets of readings can be rejected? Calculate the mean value of resistance of the resistor based on the remaining four sets of readings.

Why are coils of electric toasters and electric irons made of an alloy rather than a pure metal?

What happens when a beam of sunlight enters a dusty room through a window? Explain your answer.