An Electron Microscope Must Use Electromagnet "Lenses" Shaped Like Donuts

question 74

Multiple Choice

An electron microscope must use electromagnet "lenses" shaped like donuts to direct the electrons onto the specimen. Why?

• A) Electrons are particles but there are other particles in air as well. Without a vacuum, the electrons would strike and be scattered by the particles within the air.
• B) Electrons are highly radioactive, and the chamber must be completely sealed to prevent them from escaping and contaminating the lab area.
• C) This is the method for fixing the specimen to the slide grid for an electron microscope. Without fixing the specimen by vacuum, it would slide off and we wouldn't be able to visualize it.
• D) All of the answer choices are true.
• E) None of the answer choices is true.

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Definitions:

Variable-interval Schedule

A reinforcement strategy in operant conditioning where a response is rewarded after an unpredictable amount of time has passed.

Fixed-ratio

A type of partial reinforcement where a response is rewarded only after a specified number of responses, commonly used in behavior modification programs.

Fixed-interval

A schedule of reinforcement where the first response is rewarded only after a specified amount of time.

Variable-ratio

A schedule of reinforcement where a response is reinforced after an unpredictable number of responses, making it highly effective for maintaining behaviors.