The interior of the sun is opaque to light because it is hot enough to ionize the gas in it and photons are strongly scattered by interacting with the free electrons this produces. c) using the fact that the photons travel at the speed of light between collisions, 3 marks d) assuming that the direction of a photon after a collision is independent of its direc- the mean free path of photons in the sun is d. calculate nt), the mean number of collisions that take place in time t. tion before the collision, after a large number of collisions, n, what are i) the average displacement from its starting point, and ii) the root-mean-square distance from its starting point? 5 marks e) for a photon created by a nuclear reaction at the centre of the sun, with d 1mm, calculate how much time is needed before the root-mean-square distance is equal to 5 marks how do we know that nuclear reactions are currently taking place in the centre of 2 marks] the radius of the sun, r= 6.96 × 108 m. the sun?

Fill in the blanks with the numbers is a measure of the resistance to flow. a high liquid has a high resistance to flow and flows slowly. the ancients thought everything in the world was made of 4 we now know that there are 94 naturally occurring and scientists have created another 24 i am certain they will create even more. honey flows slowly because it has a high to flowing. a can be separated by physical means because it contains more than one pure substance and 2 pure substances are not chemically bonded to each other. a cannot be separated by physical means. all matter is made up of all elements are with the same number of protons. if it is just a single or many bonded together, if all of them have the same number of protons, it is an element. in a piece of pure iron metal, all the are joined together, that piece of iron metal is called elemental iron. a single of iron is called elemental iron. a mixture has differences from place to place. we might need a microscope to see them or they might be obvious to the unaided eye. there are surfaces separating it into different phases. a mixture is the same everywhere. it is uniform. there are no surfaces separating it into different phases. if different kinds of atoms (different elements) are bonded together by their electrons, it is called a there are physical means of to isolate the different pure substances in a mixture and there are chemical means of to isolate the different elements in a compound. 1. element 2. compound 3. mixture 4. heterogeneous 5. homogeneous 6. pure substance 7. atoms 8. separation 9. viscosity 10. resistance