2. A photon whose energy is 8.00 x 10-15 J is scattered off an electron at a 90° angle. What is the wavelength of the scattered wave? 3. A photon whose wavelength is = 5.0 x 10-11 m is scattered straight backward. What is the wavelength of the scattered wave? 4. A neutron has a mass of 1.67 x 1027 kg. Its de Broglie wavelength is 1.4 x 10-10 m. What is its kinetic energy (in eV)?