X-rays cannot pass through what?

(A) skin

(B) bone

(C) meat

(D) wood

An electron having total energy E = 4.50 eV approaches a rectangular energy barrier with U = 5.00 eV and L = 950 pm as shown in Figure P40.21. Classically, the electron cannot pass through the barrier because E < U. Quantum-mechanically, however, the probability of tunneling is not zero. (a) Calculate this probability, which is the transmission coefficient. (b) To what value would the width L of the potential barrier have to be increased for the chance of an incident 4.50-eV electron tunneling through the barrier to be one in one million?

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A. How long does it take light to travel through a 3.0 mm thick piece of glass? B. Through what thickness of water could light travel in the same amount of time?