Measuring the total width of the Moon's umbra and penumbra at EM-L2, 64,700 km, how wide would the shadow be?
The angle between the inner and outer edges of the penumbra is the same as the Sun's apparent angular diameter. At 1.0 au from the Sun, that's 32 arcmin or 0.0093 radian. At the distance from the Moon to EM-L2, this angle spans 0.0093 * 64700 km = 602 km. The Moon's diameter is 3474 km, so the umbra diameter would be 2872 km and the penumbra diameter would be 4076 km.