The best scenario to describe the doppler effect would be listening to the siren of a passing ambulance or fire truck
then it is coming towards you, the pitch is higher, it gets higher as it approaches and peaks as it gets right in front of you. then it drop at once when it passes you and continues to drop till it fades away. this is a classic descrption of the doppler effect
Johann Strauss II
hope this helps
There are no options given in respect to the question and so it is not possible to choose. I would answer this question based on my knowledge and hope it satisfies you. he form of radio active decay that would be most likely detected by you if it were happening in the room next to the one you are currently standing in is gamma.
I have learned the whole thing