# Does the frequency of a signal change when penetrating an object? [closed]

The case is I have a periodic signal with $$f_1$$. Does $$f_1$$ change? If yes, please mention all the factors that could affect $$f_1$$ ?

I know the relation:

$$u \;=\; f \;\lambda \qquad (1)$$

Is $$f_1$$ the same as the resistance in $$(2)$$ that it is independent of the voltage and current?

$$V \; = \; \frac{I}{R} \qquad (2)$$