Answer: The system internal energy is 40 Joules.
Explanation: As suggested, the formula 
should be used. 70 Joules worth of thermal energy are added, and the system does 30 Joules worth of work (energy expenditure).
==> Infrared waves from the sun, green light from the sun, and X-rays from the sun, all travel through vacuum.
==> Ocean surf waves travel through water.
==> Microwaves in an oven travel first through air, and then later through meatloaf or chicken.
==> Seismic waves (earthquakes) travel through rocks and dirt.
Answer:
Subducting convergent boundary
Explanation:
Generally, volcanoes occurs in both divergent and convergent boundaries. But the convergent boundary it occurs is usually associated with subduction.
Divergent boundary, plates move away from each other creating a new crust in the process. The diverging plates creates the space for magma to be squeezed through cracks and fissures. The magma's erupt to form volcanoes. In the Atlantic ocean the spreading of the plates causes an upwelling of magma through the crest of the Atlantic ridges. New oceanic crust are formed through this process. Sometimes the magma eruption forms volcanoes that are higher than the sea level.
Convergent boundary , plates collides with each other . But in the case of volcanoes existence , the collision should be between a denser plate(oceanic plates) and a less dense plates(continental plates) so that subduction can take place. The subducted plates (oceanic plates) creates trenches and get expose to high temperature and pressure as it sinks toward the mantle. The upper mantle rocks melts and migrate to the earth surface forming volcanoes . Over 75% of the volcanoes occur along the pacific basin where convergent boundary is dominant. Pacific ring of fire has one of the most number of volcanoes.
