Q1. A thermometer is laid out in direct sunlight. Does it measure the temperature of the air, or of the sun, or of something else? Q2. Two bodies made of the same material have the same external dimensions and appearance, but one is solid and the other is hollow. When their temperature is increased by the same amount, is the overall volume expansion the same or different. What about the size of the hole of the hollow one? Please explain I have got some others which I will ask after I get these two understood.