A video shown to the class provides some opportunity for our students to gain an understanding of key concepts visually. However teachers will not know the video's effectiveness until an actual assessment. If the student is required to study further information which is based on the video's information; and the student did not comprehend the information initially; this could have dire effects on the student's capacity to understanding subsequent information.
Chris in Science has an answer to this underlying problem... Get the students to develop a digital quiz using the video's information; and then share this quiz with others in the classroom. The cyclic rendition of knowledge being shared; strengthens the student's understanding of the content covered, but also provides opportunity for new information to be conveyed in case it was not picked up in the first place.