yes i understand that but my teacher just mailed me the question like this."Find out the sampling frequency for a video signal of bandwidth 18kHz. Give your remarks on why?" and i don't know how to solve it....

i can understand these two questions but i don,t understand the question i asked earlier...

Thanks for the detailed answer. As i mentioned that i just started this subject so i don,t really know that much its a question my teacher asked me as an assignment after the first lecture with 2 more questions as follows "How will an input image be quantized? On what factors will it depend? Will the output signal vary with reference to input signal or output signal will vary independently in terms of quantization? Q3. For an 8-connected neighbourhood, how will the pixels be arranged? Will the arrangement be same as that of 4-connected or not? Justify.