The following Lua script converts a number from base 10 to base 2:

```
-- This function takes in a number and returns its binary form as a string
function toBinary(num)
local bin = "" -- Create an empty string to store the binary form
local rem -- Declare a variable to store the remainder
-- This loop iterates over the number, dividing it by 2 and storing the remainder each time
-- It stops when the number has been divided down to 0
while num > 0 do
rem = num % 2 -- Get the remainder of the division
bin = rem .. bin -- Add the remainder to the string (in front, since we're iterating backwards)
num = math.floor(num / 2) -- Divide the number by 2
end
return bin -- Return the string
end
-- Example usage
toBinary(5) -- 101
```

This script first defines a function, to_binary, which takes a number in base 10 as its input. The function then uses a while loop to repeatedly divide the number by 2 and store the remainder in a string, bin. Finally, the function returns the string, bin.

When run, this script will print the number 10 in base 2.