The two modes of the Therac-25 are as follows: Accelerated electrons that work on _ tissue and Photons that work on _ tissue

1. The two modes of the Therac-25 are as follows: Accelerated electrons that work on shallow tissue and Photons that work on deep tissue. Accelerated electrons are used for superficial tumors because they have a limited penetration depth. Photons (X-rays) are used for deeper tumors as they can penetrate further into the tissue.

The correct option is:

• Shallow, deep

2. The '25' in Therac-25 refers to the maximum energy of the X-ray beam it could produce.

The correct option is:

• It emits 25 million electron volts