Lamps designed for different voltages have different luminous efficacy. For example, a 100-watt, 120-volt lamp will produce about 17.1 lumens per watt. A lamp with the same rated lifetime but designed for 230 V would produce only around 12.8 lumens per watt, and a similar lamp designed for 30 volts (train lighting) would produce as much as 19.8 lumens per watt. Lower voltage lamps have a thicker filament, for the same power rating. They can run hotter for the same lifetime before the filament evaporates.
How many lumens per watt does a typical train light produce?
as much as 19.8 lumens per watt

The loss of viewers continued into season seven. The premiere was down 11% among total viewers, and the results show in which Kristy Lee Cook was eliminated delivered its lowest-rated Wednesday show among the 1834 demo since the first season in 2002. However, the ratings rebounded for the season seven finale with the excitement over the battle of the Davids, and improved over season six as the series' third most watched finale. The strong finish of season seven also helped Fox become the most watched TV network in the country for the first time since its inception, a first ever in American television history for a non-Big Three major broadcast network. Overall ratings for the season were down 10% from season six, which is in line with the fall in viewership across all networks due in part to the 20072008 Writers Guild of America strike.
What was the series' third most watched finale?
season seven

The top 50 m (160 ft) of a glacier are rigid because they are under low pressure. This upper section is known as the fracture zone and moves mostly as a single unit over the plastically flowing lower section. When a glacier moves through irregular terrain, cracks called crevasses develop in the fracture zone. Crevasses form due to differences in glacier velocity. If two rigid sections of a glacier move at different speeds and directions, shear forces cause them to break apart, opening a crevasse. Crevasses are seldom more than 46 m (150 ft) deep but in some cases can be 300 m (1,000 ft) or even deeper. Beneath this point, the plasticity of the ice is too great for cracks to form. Intersecting crevasses can create isolated peaks in the ice, called seracs.
Most crevices are no deeper than what measure?
46 m (150 ft)